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drive evolution over time.",1,{"id":37,"data":38,"type":39,"maxContentLevel":19,"version":35},"ad1fce52-8413-42e8-b53b-2e1cfe28d9b4",{"type":39,"intro":40},10,[41,42],"What shape does the DNA molecule take?","How do adenine and thymine pair up in DNA?",[44,71,114,136],{"id":45,"data":46,"type":35,"maxContentLevel":19,"version":35,"reviews":49},"35204798-a95f-4187-94f7-686cf238d95c",{"type":35,"markdownContent":47,"audioMediaId":48},"As we continue exploring the fundamental concepts of biology, our focus now shifts to the mechanisms of heredity and how traits are passed down, building on our earlier exploration of cell structure and the role of DNA and RNA in encoding life’s information.\n\nIn this tile on Gene Theory, we'll first examine **DNA**: its structure, replication, and how mutations lead to genetic variation.\n\nDeoxyribonucleic acid (DNA) is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses.\n\n![Graph](image://c887d07f-a886-42bb-ac53-99a35c154ed7 \"DNA strands (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons\")\n\nTo put it simply, DNA is like a set of instructions or a blueprint that tells an organism how to grow, develop, and function.\n\nDNA’s role in biology cannot be overstated; it is the chemical basis of heredity, guiding the biological processes that maintain life from one generation to the next.","a7ef8eaf-9b43-401a-9bc9-cf037ec716b5",[50],{"id":51,"data":52,"type":53,"version":35,"maxContentLevel":19},"d89eeefd-0978-4e65-bd7e-561e1b9e9449",{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":54,"multiChoiceQuestion":58,"multiChoiceCorrect":60,"multiChoiceIncorrect":62,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":66,"matchPairsPairs":68},11,[55,56,57],"7db446df-ddf1-4b7e-b6c1-57b1c2e52432","0b38c332-add5-41d1-8b99-9d259e815a20","6f2b2400-6ffa-41b7-b6d9-5e283eb65e40",[59],"What is the mechanism of passing traits down generations called?",[61],"Heredity",[63,64,65],"Mutation","Replication","Transcription",[67],"Match the pairs below:",[69],{"left":61,"right":70,"direction":19},"Mechanism of passing traits down generations",{"id":72,"data":73,"type":35,"maxContentLevel":19,"version":25,"reviews":76},"945e6c46-d151-494b-8923-792efaeec816",{"type":35,"markdownContent":74,"audioMediaId":75},"The discovery of DNA as the hereditary material dates back to the mid-20th century, but its significance wasn’t fully understood right away.\n\nInitially, many scientists believed that proteins, not DNA, were responsible for heredity because proteins were more complex. However, as research progressed, it became clear that DNA played a crucial role in passing genetic information from one generation to the next.\n\nThe first step in understanding this came from the use of X-ray crystallography. In the early 1950s, **Rosalind Franklin**, working at King’s College London, captured critical images of DNA using this technique. Her most famous image, known as \"Photo 51,\" was taken in 1952 and provided crucial evidence that DNA had a **helical structure**.\n\n![Graph](image://e884b58e-4c9b-48d0-a982-420eda6879fd \"Rosalind Franklin by MRC Laboratory of Molecular Biology (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThe story took a controversial turn when Maurice Wilkins, a colleague of Franklin’s at King’s College, shared her X-ray data with James Watson and Francis Crick without her knowledge or permission. **Watson and Crick**, who were working at the University of Cambridge, used Franklin’s data—combined with their own research—to build the first accurate model of the DNA double helix in 1953.\n\nWhile Watson, Crick, and Wilkins were awarded the Nobel Prize in Physiology or Medicine in 1962 for their discovery, Franklin’s contributions were largely overlooked. By the time the prize was awarded, Franklin had tragically died of ovarian cancer in 1958, at the age of 37.","8b9c5a49-d386-4e45-aa2c-86bcebf5f438",[77,95],{"id":78,"data":79,"type":53,"version":25,"maxContentLevel":19},"54009495-5229-4a39-9706-68cd7abc0c9d",{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":80,"multiChoiceQuestion":83,"multiChoiceCorrect":85,"multiChoiceIncorrect":87,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":91,"matchPairsPairs":92},[81,82],"891dab6c-9fb5-4202-bcc7-e23c4b1a60b0","9dd48e65-bf2a-4aa4-83bf-ba256c112765",[84],"Who captured critical images of DNA using X-ray crystallography?",[86],"Rosalind Franklin",[88,89,90],"James Watson","Francis Crick","Maurice Wilkins",[67],[93],{"left":86,"right":94,"direction":19},"Captured critical images of DNA using X-ray crystallography",{"id":96,"data":97,"type":53,"version":35,"maxContentLevel":19},"6916fd67-6494-4325-855c-165c28a74a02",{"type":53,"reviewType":98,"spacingBehaviour":35,"orderAxisType":35,"orderQuestion":99,"orderItems":101},8,[100],"Put the following in order:",[102,105,108,111],{"label":103,"reveal":104,"sortOrder":4},"Photo 51' taken by Rosalind Franklin","1952",{"label":106,"reveal":107,"sortOrder":35},"Watson and Crick built the first accurate DNA model","1953",{"label":109,"reveal":110,"sortOrder":25},"Rosalind Franklin dies","1958",{"label":112,"reveal":113,"sortOrder":19},"Watson, Crick, and Wilkins awarded the Nobel Prize","1962",{"id":115,"data":116,"type":35,"maxContentLevel":19,"version":35,"reviews":119},"57d7d599-6d08-48db-bd6e-85a5dfb600ed",{"type":35,"markdownContent":117,"audioMediaId":118},"The **double helix** refers to the twisted ladder-like shape of the DNA molecule, where two long strands wind around each other.\n\nDNA is composed of two long strands forming a double helix, with each strand consisting of a sugar-phosphate backbone and nitrogenous bases (adenine, thymine, cytosine, and guanine) paired together through hydrogen bonds.\n\n![Graph](image://a717736e-2731-4728-9a31-56ae662aece6 \"DNA-structure-and-bases (Public domain), via Wikimedia Commons\")\n\nLet’s break that down:\n\nThe **sugar-phosphate backbone** is like the sides of the ladder, made up of alternating sugar (deoxyribose) and phosphate groups.\n\nThe nitrogenous bases (adenine, thymine, cytosine, and guanine) are like the rungs of the ladder. These bases pair up in a very specific way: **adenine** (A) pairs with **thymine** (T), and **cytosine** (C) pairs with **guanine** (G).\n\nThe specificity of these base pairings—adenine with thymine (A-T) and cytosine with guanine (C-G)— is crucial because it ensures that the genetic code is accurately copied during cell division.","24e5db68-ff55-4391-b7ee-dd5763484cec",[120],{"id":121,"data":122,"type":53,"version":35,"maxContentLevel":19},"32f45f37-287c-46d5-b6e5-b6002e0523c8",{"type":53,"reviewType":123,"spacingBehaviour":35,"matchPairsQuestion":124,"matchPairsPairs":126,"matchPairsShowExamples":6},6,[125],"Match the base with its pair",[127,130,133],{"left":128,"right":129,"direction":19},"Adenine","Thymine",{"left":131,"right":132,"direction":19},"Cytosine","Guanine",{"left":134,"right":135,"direction":19},"Cyronine","Not a base",{"id":137,"data":138,"type":35,"maxContentLevel":19,"version":25,"reviews":141},"7786b610-1333-4865-a23a-a846e123dacc",{"type":35,"markdownContent":139,"audioMediaId":140},"The discovery of the **double helix model** explained not only the structure of DNA and how it is stored but also how it could replicate itself, ensuring the faithful transmission of genetic information during cell division.\n\nWhen any cell prepares to divide (as it must for an organism to grow and develop), the DNA must make a copy.\n\nDuring replication, the DNA strands separate, and each strand serves as a template for the formation of a new complementary strand.\n\n![Graph](image://34c2582c-7f75-4296-883a-110341ab3d2b \"Nucleic acids - Transcription by Laboratoires Servier (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThis semi-conservative replication ensures that each daughter cell receives an identical copy of the DNA, preserving the genetic information across generations.\n\n**\"Semi-conservative\"** means that each new DNA molecule has one old strand and one new strand, which helps maintain accuracy.\n\nErrors during the replication process, though rare, can lead to **mutations**—changes in the DNA sequence that may result in variations in the organism.\n\nMutations can be thought of as \"mistakes\" in the DNA code. Some mutations are neutral, some are harmful, and occasionally, a mutation may confer an advantage, contributing to evolution over time — a process we’ll come back to in the final tile.","1cc9ff71-8420-4574-896f-ba38f961f718",[142],{"id":143,"data":144,"type":53,"version":35,"maxContentLevel":19},"08819116-3ed2-4cea-8117-6f7d8161870d",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":145,"multiChoiceCorrect":147,"multiChoiceIncorrect":149,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[146],"What does 'semi-conservative replication' mean?",[148],"Each new DNA molecule has one old strand and one new strand",[150,151,152],"Each new DNA molecule has two new strands","Each new DNA molecule has two old strands","Each new DNA molecule has one old strand and two new strands",{"id":154,"data":155,"type":25,"version":35,"maxContentLevel":19,"summaryPage":157,"introPage":165,"pages":171},"f3dc47ea-ebad-49f1-a40b-58f187f67595",{"type":25,"title":156},"Genes",{"id":158,"data":159,"type":19,"maxContentLevel":19,"version":35},"fa77ed84-d001-4a54-9165-d2eef1e2e9cb",{"type":19,"summary":160},[161,162,163,164],"Genes are DNA segments coding for proteins.","Exons are coding regions; introns are non-coding.","Regulatory sequences control gene expression.","Mutations can alter traits or cause disorders.",{"id":166,"data":167,"type":39,"maxContentLevel":19,"version":35},"1a15bf4d-a76f-448b-b974-891fcee68fe6",{"type":39,"intro":168},[169,170],"What do genes do in our bodies?","How do genes decide which proteins to make?",[172,210,244,285],{"id":173,"data":174,"type":35,"maxContentLevel":19,"version":35,"reviews":177},"b4a77973-8954-48ac-a12d-4d48270e037f",{"type":35,"markdownContent":175,"audioMediaId":176},"Building upon our understanding of DNA, we now turn our attention to genes, the specific sequences of DNA that carry the instructions for building and maintaining an organism.\n\nA gene is a segment of DNA that contains the necessary information to produce a functional product, typically a protein.\n\nProteins, as we know, are important molecules that perform a wide range of functions in the body, from building tissues to regulating processes in cells.\n\nThe most common range for the length of a human gene is typically between 3,000 to 100,000 base pairs, though genes can vary greatly in size.\n\nSome genes are as short as a few hundred base pairs, while others can span millions of base pairs.","ecaa1acc-45fa-45cc-a65c-fe886975535f",[178,189,200],{"id":179,"data":180,"type":53,"version":35,"maxContentLevel":19},"30edd417-ea2a-459c-91d3-e03dabad96a3",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":181,"multiChoiceCorrect":183,"multiChoiceIncorrect":185,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[182],"What is a gene?",[184],"A segment of DNA with information to produce a functional product",[186,187,188],"A segment of RNA with information to produce a functional product","A protein that regulates cell functions","A molecule that carries oxygen in the blood",{"id":190,"data":191,"type":53,"version":35,"maxContentLevel":19},"28e9bfc5-ff4b-4340-a1f4-da1ebe47b091",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":192,"multiChoiceCorrect":194,"multiChoiceIncorrect":196,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[193],"Genes are instructions typically used to produce which of the following?",[195],"Proteins",[197,198,199],"Lipids","Carbohydrates","Vitamins",{"id":201,"data":202,"type":53,"version":35,"maxContentLevel":19},"616ff4ab-5823-4e9a-a1bc-109fca962aea",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":203,"multiChoiceCorrect":205,"multiChoiceIncorrect":207,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[204],"What is the common range of human gene lengths?",[206],"3,000-100,000 base pairs",[208,209],"300-1000 base pairs","300,000-700,000 base pairs",{"id":211,"data":212,"type":35,"maxContentLevel":19,"version":35,"reviews":215},"5a4603c6-53f0-444b-af10-619a934c538d",{"type":35,"markdownContent":213,"audioMediaId":214},"The structure of a gene is complex, encompassing more than just a straightforward sequence of **nucleotides**.\n\nA gene is partially made up of coding regions called **exons**, which contain the instructions for making proteins.\n\nThese **exons** are transcribed into RNA and ultimately translated into proteins, playing a direct role in determining the traits of an organism.\n\n![Graph](image://ba6630d3-ec2f-4bc3-b384-0e586fcfd8e6 \"Haploid human genome sequence by NHS National Genetics and Genomics Education Centre (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nIt's also important to note that despite the vast size of the human genome, only about 2% of our DNA actually codes for proteins. The remaining 98% includes non-coding regions, and some elements of these regions are still not fully understood.\n\nNon-coding regions of genes are known as ‘**introns**’, and they appear interspersed between exons.\n\nAlthough **introns** are transcribed into RNA, they are removed before the RNA is translated into a protein, and the exons are spliced together.\n\nThis splicing actually serves an important purpose, because this splicing of exons doesn’t always have to occur in the same way.\n\nDifferent combinations of exons can be spliced together in different ways, leading to the production of different proteins from the same gene.\n\nThis ability to create multiple proteins from a single gene significantly increases the variety of proteins your body can produce, which is important for the complexity and adaptability of living organisms​","7f2998ec-d822-4a9b-aeec-04256da36021",[216,227],{"id":217,"data":218,"type":53,"version":35,"maxContentLevel":19},"6751b030-30c3-4da6-a4e4-aaaffd9ca985",{"type":53,"reviewType":123,"spacingBehaviour":35,"matchPairsQuestion":219,"matchPairsPairs":220,"matchPairsShowExamples":6},[67],[221,224],{"left":222,"right":223,"direction":19},"Exons","Coding regions of a gene",{"left":225,"right":226,"direction":19},"Introns","Non-coding regions of a gene",{"id":228,"data":229,"type":53,"version":35,"maxContentLevel":19},"97b2fd5e-26ad-453e-8155-d8e8d1f9001d",{"type":53,"reviewType":98,"spacingBehaviour":35,"orderAxisType":123,"orderQuestion":230,"orderItems":231},[100],[232,235,238,241],{"label":233,"reveal":234,"sortOrder":4},"(Transcription) Exons and introns are transcribed from DNA into RNA","1",{"label":236,"reveal":237,"sortOrder":35},"(Intron removal) Introns are cut out of RNA molecule","2",{"label":239,"reveal":240,"sortOrder":25},"(Splicing) Remaining exons are spliced together to form continuous RNA sequence","3",{"label":242,"reveal":243,"sortOrder":19},"(Translation) Exons are translated into proteins","4",{"id":245,"data":246,"type":35,"maxContentLevel":19,"version":35,"reviews":249},"37703f9e-4d41-4188-8f73-ce8bbcc56e1c",{"type":35,"markdownContent":247,"audioMediaId":248},"**Non-coding** regions of genes are not just \"junk DNA\": they include **regulatory** sequences that control the expression of these coding regions.\n\nBy ‘**gene expression**’, we mean the process by which the information in a gene is used to create a functional product, like a protein. We’ll come back to this in the following orb.\n\nThese regulatory sequences act like switches, determining when, where, and how much of a particular protein is produced.\n\n**Promoters**, **enhancers**, and **silencers** are specific DNA regulatory sequences that act as binding sites for proteins known as transcription factors. These transcription factors either promote or inhibit the transcription of the gene into RNA, depending on the needs of the cell.\n\n**Promoters** are like starting points, signaling where transcription should begin.\n\n**Enhancers** are sequences that boost the activity of promoters, increasing gene expression.\n\n**Silencers** do the opposite—they decrease gene expression.\n\nThis regulation ensures that genes are expressed at the right time and in the right cells, contributing to the proper development and function of an organism.","ef685e53-11ac-4c52-b713-062e889580bc",[250,270],{"id":251,"data":252,"type":53,"version":35,"maxContentLevel":19},"29c19352-97eb-44d7-8d09-bb322c4aeed0",{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":253,"multiChoiceQuestion":257,"multiChoiceCorrect":259,"multiChoiceIncorrect":261,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":265,"matchPairsPairs":266},[254,255,256],"361effe6-a09b-4fa4-afe4-5f2a3f873f4c","5f002250-6983-4e2c-b0ab-d59a85805d5b","7a59fe59-521a-4a47-bc5c-30bf2467fa1e",[258],"What do regulatory gene sequences control?",[260],"Gene expression",[262,263,264],"Protein synthesis","Cell division","DNA replication",[67],[267],{"left":268,"right":269,"direction":19},"Regulatory gene sequences","Controls gene expression",{"id":271,"data":272,"type":53,"version":35,"maxContentLevel":19},"9f0f9166-dee7-4265-8cda-2d51c8d8cc1d",{"type":53,"reviewType":123,"spacingBehaviour":35,"matchPairsQuestion":273,"matchPairsPairs":275,"matchPairsShowExamples":6},[274],"Match the type of regulatory sequence to its effect:",[276,279,282],{"left":277,"right":278,"direction":19},"Promoter","Acts as a starting point for transcription",{"left":280,"right":281,"direction":19},"Enhancer","Boosts activity of promoters and increases gene expression",{"left":283,"right":284,"direction":19},"Silencer","Decreases gene expression",{"id":286,"data":287,"type":35,"maxContentLevel":19,"version":35,"reviews":290},"3c2fcd28-1c72-44ce-b5cd-fd74e07705f1",{"type":35,"markdownContent":288,"audioMediaId":289},"Genes are not isolated entities; they interact with each other and with various molecular pathways to influence an organism’s phenotype, the set of observable traits.\n\n**Phenotype** includes everything from eye color to blood type—traits that you can see or measure.\n\nThis interaction between genes and the environment also plays a crucial role in how traits are expressed.\n\nMutations in genes, whether spontaneous or induced by external factors, can lead to variations in these traits.\n\n![Graph](image://4120a6de-7c66-4ac8-885f-792584e8abc9 \"Darwin Hybrid Tulip Mutation 2014-05-01 by LepoRello (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nSome mutations may have no effect, others can lead to genetic disorders, and some might even confer advantages that contribute to evolutionary change. Genetic disorders are diseases or conditions caused by alterations in the DNA.","6c2de70b-6b5d-4c89-be9e-fb67b6a3ad15",[291,307,319],{"id":55,"data":292,"type":53,"version":35,"maxContentLevel":19},{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":293,"multiChoiceQuestion":294,"multiChoiceCorrect":296,"multiChoiceIncorrect":298,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":302,"matchPairsPairs":303},[51,56,57],[295],"What is a phenotype?",[297],"The set of observable traits of an organism",[299,300,301],"The genetic makeup of an organism","The process of gene expression","The sequence of DNA in a gene",[67],[304],{"left":305,"right":306,"direction":19},"Phenotype","Set of observable traits of an organism",{"id":308,"data":309,"type":53,"version":35,"maxContentLevel":19},"81cc06d9-07b1-4027-8d44-b69a3e1c4794",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":310,"multiChoiceCorrect":312,"multiChoiceIncorrect":316,"multiChoiceMultiSelect":318,"multiChoiceRevealAnswerOption":6},[311],"Which of the following influence an organism's phenotype?",[313,314,315],"How different genes interact","How certain genes express themselves","Environmental factors (e.g. diet)",[317],"Number of chromosomes",true,{"id":320,"data":321,"type":53,"version":35,"maxContentLevel":19},"15461b45-33c9-4ff7-b354-1c5fab8864db",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":322,"multiChoiceCorrect":324,"multiChoiceIncorrect":328,"multiChoiceMultiSelect":318,"multiChoiceRevealAnswerOption":6},[323],"Which of the following are considered aspects of an organism's phenotype?",[325,326,327],"Eye color and hair color","Blood type","Behavior",[329],"Combination of genes",{"id":331,"data":332,"type":25,"version":35,"maxContentLevel":19,"summaryPage":334,"introPage":342,"pages":348},"901c2cd0-f7d5-46e4-a419-1a8fbbf7945f",{"type":25,"title":333},"Chromosomes",{"id":335,"data":336,"type":19,"maxContentLevel":19,"version":35},"60a14d61-37cd-4888-b517-ab4fc4e6ccb9",{"type":19,"summary":337},[338,339,340,341],"Chromosomes are DNA-packed structures in the cell nucleus.","Humans have 23 chromosome pairs, inheriting one from each parent.","Genes have specific loci on chromosomes, aiding genetic mapping.","Telomeres and centromeres protect and organize chromosomes.",{"id":343,"data":344,"type":39,"maxContentLevel":19,"version":35},"8317da7e-d3aa-41cb-80d2-491ec4a83d0c",{"type":39,"intro":345},[346,347],"What are chromosomes made of?","How do chromosomes ensure genetic diversity in offspring?",[349,374,426,454],{"id":350,"data":351,"type":35,"maxContentLevel":19,"version":35,"reviews":354},"6625e8de-3d0d-4501-9bc6-0efc3f9717ed",{"type":35,"markdownContent":352,"audioMediaId":353},"Having explored the structure and function of genes, the next step in understanding how genetic information is organized and transmitted is to look at **chromosomes**.\n\n**Genes**, which carry the instructions for building and maintaining an organism, are not scattered randomly within the cell but are instead meticulously organized into structures called **chromosomes**. This organization ensures that the vast amount of genetic information in our cells is both compactly stored and efficiently accessible.\n\n![Graph](image://a0f79f03-b0ae-4c06-abe1-fed216275394 \"Pairs of human chromosomes. (Public domain), via Wikimedia Commons\")\n\nChromosomes are thread-like structures located in the nucleus of each cell, composed of tightly wound DNA.\n\nIf you think of genes as individual recipes in a vast cookbook, then chromosomes are like the chapters that organize these recipes into manageable sections.\n\nIn humans, the DNA contained within chromosomes is organized into **23 pairs**, totaling 46 chromosomes. Each chromosome within a pair is inherited from one parent, so you receive 23 chromosomes from your mother and 23 from your father.\n\nThis pairing ensures that offspring have a combination of genetic material from both parents, which is the foundation of biological diversity.","8b740a61-fed5-4bd0-a048-95ae47d9f50d",[355],{"id":356,"data":357,"type":53,"version":35,"maxContentLevel":19},"4e48d196-2d73-464a-a6fa-70b9b74ace54",{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":358,"multiChoiceQuestion":362,"multiChoiceCorrect":364,"multiChoiceIncorrect":366,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":370,"matchPairsPairs":371},[359,360,361],"7eaf435d-ec13-4bfe-8a81-4c5ae58fd704","d3fc9096-e2ab-4db1-8356-0839cbc4be46","ac27cf67-00ff-4a09-96d5-f986b635e5d5",[363],"Where are chromosomes located within a cell?",[365],"Nucleus",[367,368,369],"Cytoplasm","Mitochondria","Ribosome",[67],[372],{"left":333,"right":373,"direction":19},"Located in the nucleus of each cell",{"id":375,"data":376,"type":35,"maxContentLevel":19,"version":35,"reviews":379},"93598476-19bf-475d-95c4-46cf4e287686",{"type":35,"markdownContent":377,"audioMediaId":378},"Each chromosome contains a long, continuous molecule of DNA, which is tightly coiled and condensed with the help of **histones**.\n\nThis compact structure allows the long DNA molecules to fit within the confined space of the cell nucleus. Think of it as packing a long, delicate piece of thread into a small spool to keep it organized and protected.\n\nThe DNA is wrapped around **histones** to form **nucleosomes**, which further coil and fold to create the compact structure of a chromosome.\n\n![Graph](image://1f09ebc7-a5a6-4339-b1ad-e856d14f3a12 \"Chromatin and histones (Public domain), via Wikimedia Commons\")","d0480cdc-c08b-4066-8101-ff59287790c6",[380,396,408,419],{"id":254,"data":381,"type":53,"version":35,"maxContentLevel":19},{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":382,"multiChoiceQuestion":383,"multiChoiceCorrect":385,"multiChoiceIncorrect":387,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":391,"matchPairsPairs":392},[251,255,256],[384],"Which of the below applies to histones?",[386],"They help in coiling and condensing DNA",[388,389,390],"They assist in DNA replication","They break down DNA","They transport DNA out of the nucleus",[67],[393],{"left":394,"right":395,"direction":19},"Histones","Proteins that package DNA by coiling and condensing it",{"id":397,"data":398,"type":53,"version":35,"maxContentLevel":19},"cc53ca1a-12de-4477-b182-d61b21e84caf",{"type":53,"reviewType":123,"spacingBehaviour":35,"matchPairsQuestion":399,"matchPairsPairs":400,"matchPairsShowExamples":6},[67],[401,403,406],{"left":394,"right":402,"direction":19},"Proteins DNA wraps around",{"left":404,"right":405,"direction":19}," Nucleosomes"," DNA wrapped around histones, basic unit of DNA packaging",{"left":333,"right":407,"direction":19}," Structures made of tightly coiled nucleosomes",{"id":409,"data":410,"type":53,"version":35,"maxContentLevel":19},"494cf0a6-f6aa-4082-97e7-71f37af097d6",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":411,"multiChoiceCorrect":413,"multiChoiceIncorrect":415,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[412],"How many pairs of chromosomes do humans have?",[414],"23",[416,417,418],"22","24","46",{"id":420,"data":421,"type":53,"version":35,"maxContentLevel":19},"6425a0c2-b838-48d7-ab82-e0f5ac0e378c",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":422,"multiChoiceCorrect":424,"multiChoiceIncorrect":425,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[423],"How many chromosomes does each parent contribute to their offspring?",[414],[416,417,418],{"id":427,"data":428,"type":35,"maxContentLevel":19,"version":35,"reviews":431},"dff284af-a414-4368-8f70-2e307f4fb479",{"type":35,"markdownContent":429,"audioMediaId":430},"The genes on each chromosome are arranged in a specific order, and their position on a chromosome is referred to as a **locus**.\n\nThis order is consistent across individuals of the same species, which is why scientists can map genes to specific locations on specific chromosomes.\n\nFor example, if a gene responsible for a particular trait is located near the tip of chromosome 4, it will be found in the same place in every human.\n\nThis consistency allows scientists to precisely identify and study the genetic basis of various traits.\n\n![Graph](image://8f1da74f-563c-4a75-9e38-8f3606b983a2 \"Disease Gene Mapping with Multiple Chromosomes. Image by Esherma1 (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")","9880ce86-a76b-4af5-b4d1-be52f6b6c85f",[432,443],{"id":433,"data":434,"type":53,"version":35,"maxContentLevel":19},"8fd68b3e-40f4-48c3-927f-cf70a8fea23c",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":435,"multiChoiceCorrect":437,"multiChoiceIncorrect":441,"multiChoiceMultiSelect":318,"multiChoiceRevealAnswerOption":6},[436],"What is consistent across individuals of the same species regarding chromosomes?",[438,439,440],"Gene order","Chromosome length","Chromosome number",[442],"Telomeres",{"id":444,"data":445,"type":53,"version":35,"maxContentLevel":19},"9e14604d-c126-4188-b37a-6f2556db0f60",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":446,"multiChoiceCorrect":448,"multiChoiceIncorrect":450,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[447],"What is the specific position of genes on a chromosome called?",[449],"Locus",[451,452,453],"Gene map","Locality","Gene cluster",{"id":455,"data":456,"type":35,"maxContentLevel":19,"version":35,"reviews":459},"abf72237-3eb0-4465-ad03-3ea3d765a701",{"type":35,"markdownContent":457,"audioMediaId":458},"Chromosomes also contain regions that do not code for proteins but are essential for maintaining chromosome integrity and regulating gene expression.\n\n![Graph](image://097cc366-61e2-4a9c-9124-8313cc55696b \"Telomeres by AJC1 (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\n**Telomeres**, for instance (which you can see above), are repetitive sequences at the ends of chromosomes that protect them from degradation, much like the plastic tips on shoelaces prevent them from fraying.\n\n**Centromeres**, located near the center of chromosomes, are essential for the proper segregation of chromosomes during cell division, ensuring that each daughter cell receives the correct number of chromosomes.\n\nDuring **cell division**, chromosomes play a crucial role in ensuring that genetic information is accurately passed on to daughter cells.\n\nWhen a cell divides, its chromosomes are duplicated, and each new cell receives an identical set of chromosomes.\n\nDuring **mitosis**, this ensures that every cell in your body has the same genetic information.\n\nHowever, as you may remember from an earlier orb, in reproductive cells, a different type of cell division called **meiosis** occurs, reducing the chromosome number by half so that when fertilization happens, the resulting zygote has the correct number of chromosomes—restoring the full set of 46 in humans.","bb86dda8-dcd8-47e7-992d-4f8e9393ffaa",[460,472,479],{"id":461,"data":462,"type":53,"version":35,"maxContentLevel":19},"45725716-2652-49c5-8217-60b9fc00facb",{"type":53,"reviewType":123,"spacingBehaviour":35,"matchPairsQuestion":463,"matchPairsPairs":465,"matchPairsShowExamples":6},[464],"Match the biological event to its consequences, in terms of chromosomes:",[466,469],{"left":467,"right":468,"direction":19},"Cell division (mitosis)","Chromosomes are duplicated to ensure identical genetic information",{"left":470,"right":471,"direction":19},"Fertilization"," Restores a full set of chromosomes (46 in humans) by the fusion of two haploid cells (sperm and egg, each with 23 chromosomes)",{"id":473,"data":474,"type":53,"version":35,"maxContentLevel":19},"f9b4500a-23e3-4b7a-ae13-5354aa2d8f74",{"type":53,"reviewType":35,"spacingBehaviour":35,"activeRecallQuestion":475,"activeRecallAnswers":477},[476],"What is the function of telomeres (the repetitive sequences at the ends of chromosomes)?",[478],"Protect chromosomes from degradation (like the ends of a shoelace)",{"id":255,"data":480,"type":53,"version":35,"maxContentLevel":19},{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":481,"multiChoiceQuestion":482,"multiChoiceCorrect":484,"multiChoiceIncorrect":486,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":490,"matchPairsPairs":491},[251,254,256],[483],"What role do centromeres (located near the center of chromosomes) play during cell division?",[485],"Ensures the proper segregation of chromosomes",[487,488,489],"Assist in DNA replication","Protect chromosome ends","Facilitate gene expression",[67],[492],{"left":493,"right":494,"direction":19},"Centromeres","Middle chromosome sections essential for proper segregation in division",{"id":496,"data":497,"type":25,"version":499,"maxContentLevel":19,"summaryPage":500,"introPage":508,"pages":514},"1a0e4eb2-c564-497a-9763-dac3cf9d8860",{"type":25,"title":498},"Gene Expression",4,{"id":501,"data":502,"type":19,"maxContentLevel":19,"version":35},"aecf1591-4c11-4edd-9b20-3665fad8e59b",{"type":19,"summary":503},[504,505,506,507],"DNA is a cookbook; genes are recipes.","mRNA carries DNA instructions to ribosomes.","Ribosomes translate mRNA into proteins.","Gene expression is tightly regulated and adaptable.",{"id":509,"data":510,"type":39,"maxContentLevel":19,"version":35},"c7da6d9b-489d-4e1b-9a4e-d05e78985120",{"type":39,"intro":511},[512,513],"What are Mendel's laws of inheritance?","How do Mendel's laws explain trait transmission from parents to offspring?",[515,536,555,575,588],{"id":516,"data":517,"type":35,"maxContentLevel":19,"version":19,"reviews":520},"3c3c011c-7dc2-4bf3-9a10-21e920077529",{"type":35,"markdownContent":518,"audioMediaId":519},"**Gene expression** is the process by which the information encoded in DNA is used to produce the observable traits of an organism.\n\nThis concept is central to understanding how the instructions in our genes are translated into the proteins that perform almost every function in the body.\n\nTo grasp gene expression, we need to start with the central dogma of molecular biology, which outlines the flow of genetic information from DNA to RNA to protein.\n\nThe process begins with transcription, where the **DNA sequence of a gene is copied into messenger RNA (mRNA).**\n\n![Graph](image://fbdd9aec-178b-42f8-9435-ad0efa4c4f4b \"TranscriptionGraphic PublicDomain (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons\")","afddabe2-3a2b-4560-9c4c-11e97f80316b",[521],{"id":522,"data":523,"type":53,"version":19,"maxContentLevel":19},"acc126f4-f4be-49fe-93e8-bf0bb1d63665",{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":524,"multiChoiceQuestion":527,"multiChoiceCorrect":529,"multiChoiceIncorrect":530,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":532,"matchPairsPairs":533},[525,526],"9e2f6961-631b-4228-afd9-cb482088e9e7","a5e10126-8afd-4725-beb2-29b0bc91d4b5",[528],"What is the process by which DNA information leads to observable traits?",[498],[65,531,64],"Translation",[67],[534],{"left":498,"right":535,"direction":19},"Process by which DNA information produces observable traits",{"id":537,"data":538,"type":35,"maxContentLevel":19,"version":35,"reviews":541},"a48e63ba-517f-4425-b52e-83e5ea0b1854",{"type":35,"markdownContent":539,"audioMediaId":540},"Imagine DNA as a large cookbook, and each gene as a specific recipe within it.\n\n**Transcription** is like copying one of these recipes onto a separate sheet of paper—this sheet is the mRNA, which will carry the instructions out of the DNA “cookbook” and into the cell’s kitchen.\\\n\\\n**Transcription** is initiated when an enzyme called **RNA polymerase** binds to a specific region of the DNA, known as the promoter, which signals the start of the gene.\n\n**RNA polymerase** unwinds the DNA helix and creates a complementary strand of mRNA by matching RNA nucleotides to the DNA template.\n\n![Graph](image://c8f713a4-6965-43b6-ab48-93f908ab5427 \"Image: Genomics Education Programme, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nUnlike DNA, where adenine (A) pairs with thymine (T), in RNA, adenine pairs with uracil (U).\n\nThis newly formed mRNA strand is like a portable recipe, ready to be used outside the nucleus of the cell.","f43c879b-adb0-4b39-a47c-5f140e780042",[542],{"id":543,"data":544,"type":53,"version":35,"maxContentLevel":19},"d9389d7a-037a-4cf5-a04b-20bd3e9b0e97",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":545,"multiChoiceCorrect":547,"multiChoiceIncorrect":551,"multiChoiceMultiSelect":318,"multiChoiceRevealAnswerOption":6},[546],"Which three actions are performed by RNA Polymerase during transcription?",[548,549,550],"Binds to promoter to initiate transcription (step 1)","Unwinds DNA helix (step 2)","Creates complementary mRNA strand (step 3)",[552,553,554],"Splices RNA (step 2)","Translates mRNA (step 2)","Adds amino acids to protein chain (step 3)",{"id":556,"data":557,"type":35,"maxContentLevel":19,"version":25,"reviews":560},"1ed32f81-cadf-4fd3-95be-af8670e34524",{"type":35,"markdownContent":558,"audioMediaId":559},"After transcription, once the mRNA is synthesized, it undergoes **processing**. This involves removing **introns**—non-coding sections of RNA—and splicing together **exons**, the coding regions that will be used to build the protein.\n\n![Graph](image://ff400c8d-f1f1-4ecb-8227-80e95384a618 \"DNA exons and introns splicing process. Image (Public domain), via Wikimedia Commons\")\n\nThe processed mRNA then exits the nucleus and enters the cytoplasm, where it meets the cell's **ribosomes**.\n\nThink of ribosomes as chefs in the cell’s kitchen, responsible for reading the mRNA \"recipe\" and assembling the protein.\n\nIn the **translation** stage, the ribosome reads the mRNA sequence and translates it into a chain of **amino acids**, the building blocks of proteins.","e0849fce-6587-4a8e-8dc0-3e8a46be79f0",[561],{"id":562,"data":563,"type":53,"version":35,"maxContentLevel":19},"a6273a13-62ed-44b4-90ec-48294b4b7d34",{"type":53,"reviewType":98,"spacingBehaviour":35,"orderAxisType":123,"orderQuestion":564,"orderItems":566},[565],"What happens after transcription, once the mRNA is synthesized?",[567,569,571,573],{"label":568,"reveal":234,"sortOrder":4},"mRNA undergoes processing (removing introns and splicing together exons)",{"label":570,"reveal":237,"sortOrder":35},"mRNA exits the nucleus and enters cytoplasm",{"label":572,"reveal":240,"sortOrder":25},"mRNA encounters ribosomes",{"label":574,"reveal":243,"sortOrder":19},"Ribosomes 'translate' mRNA sequence into amino acids",{"id":576,"data":577,"type":35,"maxContentLevel":19,"version":35,"reviews":580},"7fdc8e59-8be0-4a13-963e-d4e9c1db453b",{"type":35,"markdownContent":578,"audioMediaId":579},"During **translation**, transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together in a particular order.\n\nThe **Transfer RNA** (tRNA) molecules know the correct order in which to bring amino acids to the ribosome because they follow the sequence of codons in the mRNA.\n\n![Graph](image://2c1750c3-690b-43a5-88cd-eb11a0398229 \"Transcription and translation. Image: NHS National Genetics and Genomics Education Centre, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\n**Codons** are groups of three nucleotides in the mRNA that specify which amino acid should be added next.\n\nThe growing chain of amino acids eventually folds into a functional protein, ready to carry out its role in the cell.","e97c2516-dbd6-4a39-892b-28a8dea4f3af",[581],{"id":582,"data":583,"type":53,"version":35,"maxContentLevel":19},"153e1f3f-0781-44ca-8cbb-74a67454a79a",{"type":53,"reviewType":499,"spacingBehaviour":35,"clozeQuestion":584,"clozeWords":586},[585],"Transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together in a particular order.",[587],"amino acids",{"id":589,"data":590,"type":35,"maxContentLevel":19,"version":35,"reviews":593},"317e1419-c678-491c-ac2d-fd7f65660cee",{"type":35,"markdownContent":591,"audioMediaId":592},"**Gene expression** is one-way directed process, though not a simple one; it is carefully regulated at multiple stages to ensure that proteins are produced at the right time, in the right place, and in the right amounts.\n\nAdditionally, other mechanisms like regulatory RNAs and epigenetic modifications can fine-tune the expression of genes in response to the cell’s needs or environmental changes.\n\n**Epigenetic modifications** involve changes that affect gene expression without altering the DNA sequence itself. A common example is the addition of a chemical group called a methyl group to DNA, which can turn a gene off or reduce its activity.\n\n![Graph](image://01b6b043-348d-4e99-97c5-663c832b0b67 \"Epigenetic mechanisms (Public domain), via Wikimedia Commons\")\n\nFor example, in response to chronic stress, **methyl groups** may be added to genes involved in stress regulation, lowering their activity. This could be the body's way of adapting to prolonged stress by lessening the impact of stress hormones.\n\nThis tightly regulated process of gene expression is also the foundation of many modern biotechnologies, such as genetic engineering and gene therapy, which aim to manipulate gene expression to treat genetic disorders by restoring the proper levels of key proteins.","279e2a7f-1e65-4426-948c-fbbb415856d2",[594,608],{"id":595,"data":596,"type":53,"version":35,"maxContentLevel":19},"1935280b-4ad2-4d56-9da4-fd7e3747d2c9",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":597,"multiChoiceCorrect":599,"multiChoiceIncorrect":603,"multiChoiceMultiSelect":318,"multiChoiceRevealAnswerOption":6},[598],"Which of the following apply to the concept of epigenetic modification?",[600,601,602],"Changes affecting gene expression without altering the DNA sequence","Example: addition of chemical groups like methyl groups to DNA","Can turn genes off or reduce their activity",[604,605,606,607],"Changes in DNA sequence","Direct protein synthesis","RNA splicing","Example: insertion of a mutation in the DNA sequence",{"id":609,"data":610,"type":53,"version":35,"maxContentLevel":19},"c2e10806-0202-4d7a-b912-291dafe600e5",{"type":53,"reviewType":123,"spacingBehaviour":35,"matchPairsQuestion":611,"matchPairsPairs":613,"matchPairsShowExamples":6},[612],"Match the gene expression process to its description:",[614,616],{"left":65,"right":615,"direction":19},"DNA is copied into mRNA in the nucleus.",{"left":531,"right":617,"direction":19},"mRNA is decoded to assemble proteins in the ribosome",{"id":619,"data":620,"type":25,"version":35,"maxContentLevel":19,"summaryPage":621,"introPage":629,"pages":635},"bac2070a-c8a6-435a-abca-b794f31d325e",{"type":25,"title":61},{"id":622,"data":623,"type":19,"maxContentLevel":19,"version":35},"47c8c166-715a-489f-b6cc-783c6bbc1ec8",{"type":19,"summary":624},[625,626,627,628],"Genes are organized into pairs called alleles.","Dominant alleles mask recessive ones in traits.","Alleles separate during gamete formation, restoring pairs in offspring.","Traits are inherited independently, following Mendel's laws.",{"id":630,"data":631,"type":39,"maxContentLevel":19,"version":35},"18a99d82-6673-4014-a65a-58e302bd414d",{"type":39,"intro":632},[633,634],"How do dominant alleles affect an organism's traits?","What role do alleles play in determining phenotype?",[636,653,690,728],{"id":637,"data":638,"type":35,"maxContentLevel":19,"version":35,"reviews":641},"2569ebed-20d8-4a51-977e-00d975519daf",{"type":35,"markdownContent":639,"audioMediaId":640},"With a solid understanding of how genes are organized into chromosomes and how they function within cells, we can now explore how these genes are passed from one generation to the next—a process known as **heredity**.\n\nHeredity is the mechanism by which genetic information is transmitted from parents to offspring, ensuring the continuity of life and the preservation of traits within a species.\n\nThe foundational principles of heredity were first uncovered by **Gregor Mendel**, a 19th-century scientist often referred to as the \"father of modern genetics.\"\n\n![Graph](image://c936a398-f78c-43cf-973a-da6657216bb6 \"Gregor Mendel (Public domain), via Wikimedia Commons\")\n\n**Mendel** discovered these patterns through meticulous experiments with pea plants, Mendel discovered that traits are inherited in specific, predictable patterns, governed by what we now understand to be genes.\n\n![Graph](image://d6b8eb67-9a35-4191-8080-86b82ddc6fad \"Doperwt rijserwt peulen Pisum sativum by Rasbak (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nThese **laws of heredity** laid the groundwork for modern genetics by establishing the idea that genes are the fundamental units of inheritance, passed from parents to offspring in a predictable manner.\n\nThe discovery of chromosomes as the carriers of genes later confirmed and expanded on Mendel’s principles, integrating them into the broader framework of molecular biology.","de63142f-c57c-4e20-9735-d44ce2796695",[642],{"id":643,"data":644,"type":53,"version":35,"maxContentLevel":19},"b86bd8fb-6b89-42f4-868c-0b5b82e5a88e",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":645,"multiChoiceCorrect":647,"multiChoiceIncorrect":649,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[646],"What did Gregor Mendel use in his experiments to discover the principles of heredity?",[648],"Pea plants",[650,651,652],"Fruit flies","Corn plants","Mice",{"id":654,"data":655,"type":35,"maxContentLevel":19,"version":35,"reviews":658},"8e88392d-7705-433b-b55e-2b130cd9fbb8",{"type":35,"markdownContent":656,"audioMediaId":657},"One of Mendel’s key discoveries was the concept that **genes exist in pairs**, with each parent contributing one 'version' of that gene to their offspring. These pairs of genes are known as alleles, and they can be either **dominant** or **recessive**.\n\nThis principle is known as Mendel’s **Third Law of Dominance**.\n\nA **dominant allele** is like the louder voice in a pair—it tends to express itself in the organism’s traits, even if the other allele (from the other parent) is different.\n\nFor instance, if the allele for **purple flower** color is **dominant**, a pea plant with one purple flower allele and one white flower allele will still have purple flowers because the dominant purple allele \"masks\" the presence of the recessive white allele.\n\n![Graph](image://2a58dca5-8ff6-402c-8d30-1ad3f04d72fe \"Pisum sativum biflorum1 (Public domain), via Wikimedia Commons\")\n\nA **recessive allele** is quieter and will only express itself in the organism’s traits if both alleles for that trait are recessive.\n\nIn our example, the white flower color would only appear if the pea plant inherited the white allele from both parents. But if it appeared alongside a dominant purple the white allele would remain hidden, but could still be passed on to the next generation.\n\nSo, if a pea plant carries one allele for purple flowers (dominant) and one for white flowers (recessive), the dominant purple allele will determine the flower color, while the white allele remains hidden but can still be passed on to the next generation.","f82fa619-a345-4e95-8d02-e94fd5155302",[659,674],{"id":256,"data":660,"type":53,"version":35,"maxContentLevel":19},{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":661,"multiChoiceQuestion":662,"multiChoiceCorrect":664,"multiChoiceIncorrect":666,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":670,"matchPairsPairs":671},[251,254,255],[663],"What are alleles?",[665],"Versions of genes contributed by each parent",[667,668,669],"Single genes inherited from one parent","Proteins that determine traits","Chromosomes that carry genetic information",[67],[672],{"left":673,"right":665,"direction":19},"Alleles",{"id":56,"data":675,"type":53,"version":35,"maxContentLevel":19},{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":676,"multiChoiceQuestion":677,"multiChoiceCorrect":679,"multiChoiceIncorrect":681,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":685,"matchPairsPairs":686},[51,55,57],[678],"When does a recessive allele express itself in an organism's traits?",[680],"Only if both alleles for that trait are recessive",[682,683,684],"When it is paired with a dominant allele","When it is inherited from the mother","When it is inherited from the father",[67],[687],{"left":688,"right":689,"direction":19},"Recessive Allele","Expresses traits only when present in two copies",{"id":691,"data":692,"type":35,"maxContentLevel":19,"version":35,"reviews":695},"600c723e-1e49-49ce-ad52-4abdaa85458d",{"type":35,"markdownContent":693,"audioMediaId":694},"Mendel’s first law, **the Law of Segregation**, explains how these alleles are separated during the formation of gametes—sperm and egg cells—so that each gamete carries only one allele for each trait.\n\nWhen fertilization occurs, the offspring inherits one allele from each parent, restoring the pair.\n\n![Graph](image://f9f29b34-32ad-47d2-ab3b-76da6a380795 \"Sperm-egg (Public domain), via Wikimedia Commons\")\n\nAnother key principle Mendel discovered is the **Law of Independent Assortment**, which explains how different traits are inherited independently of one another.\n\nThis law states that the **alleles for different traits** segregate independently during the formation of gametes.\n\nAs a result, the inheritance of one trait (such as flower color) does not influence the inheritance of another (such as seed shape).\n\nThis principle applies primarily to genes located on different chromosomes or far apart on the same chromosome.\n\nMendel’s experiments showed that when crossing plants with two different traits, the offspring exhibited combinations of traits in ratios that could be mathematically predicted, demonstrating the independent nature of allele assortment.","255d221f-5cf9-439a-9191-916508b4e10e",[696,707,718],{"id":697,"data":698,"type":53,"version":35,"maxContentLevel":19},"214216aa-960c-4775-ac6c-33715dbdd341",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":699,"multiChoiceCorrect":701,"multiChoiceIncorrect":703,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[700],"What does the Law of Segregation explain?",[702],"The separation of alleles during gamete formation",[704,705,706],"The dominance of certain alleles","The independent assortment of traits","The inheritance of linked genes",{"id":708,"data":709,"type":53,"version":35,"maxContentLevel":19},"d0d2429b-2eee-4bf9-8a71-cae9b711ce56",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":710,"multiChoiceCorrect":712,"multiChoiceIncorrect":714,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[711],"What do gametes carry, in terms of alleles?",[713],"One allele for each trait",[715,716,717],"Two alleles for each trait","Only dominant alleles","Only recessive alleles",{"id":719,"data":720,"type":53,"version":35,"maxContentLevel":19},"476a99d1-b015-4fee-82d5-04317c316e04",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":721,"multiChoiceCorrect":723,"multiChoiceIncorrect":725,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[722],"Mendel's Law of Independent Assortment states that alleles for different traits segregate independently. What does this mean for heredity?",[724],"Offspring can inherit different combinations of traits from each parent",[726,727],"Groups of traits are inherited in specific bundles from one parent","Traits are inherited randomly, with no rules governing how they are inherited",{"id":729,"data":730,"type":35,"maxContentLevel":19,"version":35,"reviews":733},"db075717-c5f4-4043-b65a-acd05e14a02f",{"type":35,"markdownContent":731,"audioMediaId":732},"\nAs well as introducing the concept of dominant and recessive traits, Mendel’s work laid the foundation for the concepts of **genotype** and **phenotype**.\n\nThe **genotype** refers to the genetic makeup of an organism—the specific combination of alleles it possesses.\n\nThe **phenotype** is the observable expression of these traits—what we can actually see, such as eye color or height.\n\n![Graph](image://3da0b941-010c-4139-9ac8-065324b204da \"Coquina variation in phenotype. Image by Debivort (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nWhile the genotype determines the potential for a trait, the phenotype can be influenced by interactions between different alleles, as well as environmental factors.\n\nFor example, even if someone has the genetic potential for tall stature (genotype), factors like nutrition during growth years can influence the actual height (phenotype).\n\nThe principles of Mendel’s laws apply universally to all sexually reproducing organisms, from plants to animals to humans.\n\nThey form the basis for understanding not only simple inheritance patterns but also more complex phenomena such as genetic disorders, polygenic traits (traits controlled by multiple genes), and the role of genetic variation in evolution.\n\nHeredity is the engine of **evolution**—and this will be the topic of our final orb.","de129801-5e4d-4469-8dd4-97c5ecde6156",[734,745],{"id":735,"data":736,"type":53,"version":35,"maxContentLevel":19},"365d4143-2626-441b-8db5-a3c994cfe8d1",{"type":53,"reviewType":19,"spacingBehaviour":35,"multiChoiceQuestion":737,"multiChoiceCorrect":739,"multiChoiceIncorrect":741,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[738],"What influences the phenotype of an organism?",[740],"Genotype and environmental factors",[742,743,744],"Only genotype","Only environmental factors","Neither genotype nor environmental factors",{"id":57,"data":746,"type":53,"version":35,"maxContentLevel":19},{"type":53,"reviewType":19,"spacingBehaviour":35,"collapsingSiblings":747,"multiChoiceQuestion":748,"multiChoiceCorrect":750,"multiChoiceIncorrect":752,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":755,"matchPairsPairs":756},[51,55,56],[749],"What are polygenic traits?",[751],"Traits controlled by multiple genes",[753,754],"Traits influenced by the environment","Traits that are always dominant",[67],[757],{"left":758,"right":751,"direction":19},"Polygenic Traits",[760,1033,1304,1545,1843],{"id":23,"data":24,"type":25,"version":19,"maxContentLevel":19,"summaryPage":27,"introPage":36,"pages":761},[762,816,876,963],{"id":45,"data":46,"type":35,"maxContentLevel":19,"version":35,"reviews":49,"parsed":763},{"data":764,"body":767,"toc":814},{"title":765,"description":766},"","As we continue exploring the fundamental concepts of biology, our focus now shifts to the mechanisms of heredity and how traits are passed down, building on our earlier exploration of cell structure and the role of DNA and RNA in encoding life’s information.",{"type":768,"children":769},"root",[770,777,789,794,804,809],{"type":771,"tag":772,"props":773,"children":774},"element","p",{},[775],{"type":776,"value":766},"text",{"type":771,"tag":772,"props":778,"children":779},{},[780,782,787],{"type":776,"value":781},"In this tile on Gene Theory, we'll first examine ",{"type":771,"tag":783,"props":784,"children":785},"strong",{},[786],{"type":776,"value":26},{"type":776,"value":788},": its structure, replication, and how mutations lead to genetic variation.",{"type":771,"tag":772,"props":790,"children":791},{},[792],{"type":776,"value":793},"Deoxyribonucleic acid (DNA) is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses.",{"type":771,"tag":772,"props":795,"children":796},{},[797],{"type":771,"tag":798,"props":799,"children":803},"img",{"alt":800,"src":801,"title":802},"Graph","image://c887d07f-a886-42bb-ac53-99a35c154ed7","DNA strands (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":805,"children":806},{},[807],{"type":776,"value":808},"To put it simply, DNA is like a set of instructions or a blueprint that tells an organism how to grow, develop, and function.",{"type":771,"tag":772,"props":810,"children":811},{},[812],{"type":776,"value":813},"DNA’s role in biology cannot be overstated; it is the chemical basis of heredity, guiding the biological processes that maintain life from one generation to the next.",{"title":765,"searchDepth":25,"depth":25,"links":815},[],{"id":72,"data":73,"type":35,"maxContentLevel":19,"version":25,"reviews":76,"parsed":817},{"data":818,"body":820,"toc":874},{"title":765,"description":819},"The discovery of DNA as the hereditary material dates back to the mid-20th century, but its significance wasn’t fully understood right away.",{"type":768,"children":821},[822,826,831,849,857,869],{"type":771,"tag":772,"props":823,"children":824},{},[825],{"type":776,"value":819},{"type":771,"tag":772,"props":827,"children":828},{},[829],{"type":776,"value":830},"Initially, many scientists believed that proteins, not DNA, were responsible for heredity because proteins were more complex. However, as research progressed, it became clear that DNA played a crucial role in passing genetic information from one generation to the next.",{"type":771,"tag":772,"props":832,"children":833},{},[834,836,840,842,847],{"type":776,"value":835},"The first step in understanding this came from the use of X-ray crystallography. In the early 1950s, ",{"type":771,"tag":783,"props":837,"children":838},{},[839],{"type":776,"value":86},{"type":776,"value":841},", working at King’s College London, captured critical images of DNA using this technique. Her most famous image, known as \"Photo 51,\" was taken in 1952 and provided crucial evidence that DNA had a ",{"type":771,"tag":783,"props":843,"children":844},{},[845],{"type":776,"value":846},"helical structure",{"type":776,"value":848},".",{"type":771,"tag":772,"props":850,"children":851},{},[852],{"type":771,"tag":798,"props":853,"children":856},{"alt":800,"src":854,"title":855},"image://e884b58e-4c9b-48d0-a982-420eda6879fd","Rosalind Franklin by MRC Laboratory of Molecular Biology (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":858,"children":859},{},[860,862,867],{"type":776,"value":861},"The story took a controversial turn when Maurice Wilkins, a colleague of Franklin’s at King’s College, shared her X-ray data with James Watson and Francis Crick without her knowledge or permission. ",{"type":771,"tag":783,"props":863,"children":864},{},[865],{"type":776,"value":866},"Watson and Crick",{"type":776,"value":868},", who were working at the University of Cambridge, used Franklin’s data—combined with their own research—to build the first accurate model of the DNA double helix in 1953.",{"type":771,"tag":772,"props":870,"children":871},{},[872],{"type":776,"value":873},"While Watson, Crick, and Wilkins were awarded the Nobel Prize in Physiology or Medicine in 1962 for their discovery, Franklin’s contributions were largely overlooked. By the time the prize was awarded, Franklin had tragically died of ovarian cancer in 1958, at the age of 37.",{"title":765,"searchDepth":25,"depth":25,"links":875},[],{"id":115,"data":116,"type":35,"maxContentLevel":19,"version":35,"reviews":119,"parsed":877},{"data":878,"body":880,"toc":961},{"title":765,"description":879},"The double helix refers to the twisted ladder-like shape of the DNA molecule, where two long strands wind around each other.",{"type":768,"children":881},[882,894,899,907,912,923,956],{"type":771,"tag":772,"props":883,"children":884},{},[885,887,892],{"type":776,"value":886},"The ",{"type":771,"tag":783,"props":888,"children":889},{},[890],{"type":776,"value":891},"double helix",{"type":776,"value":893}," refers to the twisted ladder-like shape of the DNA molecule, where two long strands wind around each other.",{"type":771,"tag":772,"props":895,"children":896},{},[897],{"type":776,"value":898},"DNA is composed of two long strands forming a double helix, with each strand consisting of a sugar-phosphate backbone and nitrogenous bases (adenine, thymine, cytosine, and guanine) paired together through hydrogen bonds.",{"type":771,"tag":772,"props":900,"children":901},{},[902],{"type":771,"tag":798,"props":903,"children":906},{"alt":800,"src":904,"title":905},"image://a717736e-2731-4728-9a31-56ae662aece6","DNA-structure-and-bases (Public domain), via Wikimedia Commons",[],{"type":771,"tag":772,"props":908,"children":909},{},[910],{"type":776,"value":911},"Let’s break that down:",{"type":771,"tag":772,"props":913,"children":914},{},[915,916,921],{"type":776,"value":886},{"type":771,"tag":783,"props":917,"children":918},{},[919],{"type":776,"value":920},"sugar-phosphate backbone",{"type":776,"value":922}," is like the sides of the ladder, made up of alternating sugar (deoxyribose) and phosphate groups.",{"type":771,"tag":772,"props":924,"children":925},{},[926,928,933,935,940,942,947,949,954],{"type":776,"value":927},"The nitrogenous bases (adenine, thymine, cytosine, and guanine) are like the rungs of the ladder. These bases pair up in a very specific way: ",{"type":771,"tag":783,"props":929,"children":930},{},[931],{"type":776,"value":932},"adenine",{"type":776,"value":934}," (A) pairs with ",{"type":771,"tag":783,"props":936,"children":937},{},[938],{"type":776,"value":939},"thymine",{"type":776,"value":941}," (T), and ",{"type":771,"tag":783,"props":943,"children":944},{},[945],{"type":776,"value":946},"cytosine",{"type":776,"value":948}," (C) pairs with ",{"type":771,"tag":783,"props":950,"children":951},{},[952],{"type":776,"value":953},"guanine",{"type":776,"value":955}," (G).",{"type":771,"tag":772,"props":957,"children":958},{},[959],{"type":776,"value":960},"The specificity of these base pairings—adenine with thymine (A-T) and cytosine with guanine (C-G)— is crucial because it ensures that the genetic code is accurately copied during cell division.",{"title":765,"searchDepth":25,"depth":25,"links":962},[],{"id":137,"data":138,"type":35,"maxContentLevel":19,"version":25,"reviews":141,"parsed":964},{"data":965,"body":967,"toc":1031},{"title":765,"description":966},"The discovery of the double helix model explained not only the structure of DNA and how it is stored but also how it could replicate itself, ensuring the faithful transmission of genetic information during cell division.",{"type":768,"children":968},[969,981,986,991,999,1004,1014,1026],{"type":771,"tag":772,"props":970,"children":971},{},[972,974,979],{"type":776,"value":973},"The discovery of the ",{"type":771,"tag":783,"props":975,"children":976},{},[977],{"type":776,"value":978},"double helix model",{"type":776,"value":980}," explained not only the structure of DNA and how it is stored but also how it could replicate itself, ensuring the faithful transmission of genetic information during cell division.",{"type":771,"tag":772,"props":982,"children":983},{},[984],{"type":776,"value":985},"When any cell prepares to divide (as it must for an organism to grow and develop), the DNA must make a copy.",{"type":771,"tag":772,"props":987,"children":988},{},[989],{"type":776,"value":990},"During replication, the DNA strands separate, and each strand serves as a template for the formation of a new complementary strand.",{"type":771,"tag":772,"props":992,"children":993},{},[994],{"type":771,"tag":798,"props":995,"children":998},{"alt":800,"src":996,"title":997},"image://34c2582c-7f75-4296-883a-110341ab3d2b","Nucleic acids - Transcription by Laboratoires Servier (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":1000,"children":1001},{},[1002],{"type":776,"value":1003},"This semi-conservative replication ensures that each daughter cell receives an identical copy of the DNA, preserving the genetic information across generations.",{"type":771,"tag":772,"props":1005,"children":1006},{},[1007,1012],{"type":771,"tag":783,"props":1008,"children":1009},{},[1010],{"type":776,"value":1011},"\"Semi-conservative\"",{"type":776,"value":1013}," means that each new DNA molecule has one old strand and one new strand, which helps maintain accuracy.",{"type":771,"tag":772,"props":1015,"children":1016},{},[1017,1019,1024],{"type":776,"value":1018},"Errors during the replication process, though rare, can lead to ",{"type":771,"tag":783,"props":1020,"children":1021},{},[1022],{"type":776,"value":1023},"mutations",{"type":776,"value":1025},"—changes in the DNA sequence that may result in variations in the organism.",{"type":771,"tag":772,"props":1027,"children":1028},{},[1029],{"type":776,"value":1030},"Mutations can be thought of as \"mistakes\" in the DNA code. Some mutations are neutral, some are harmful, and occasionally, a mutation may confer an advantage, contributing to evolution over time — a process we’ll come back to in the final tile.",{"title":765,"searchDepth":25,"depth":25,"links":1032},[],{"id":154,"data":155,"type":25,"version":35,"maxContentLevel":19,"summaryPage":157,"introPage":165,"pages":1034},[1035,1067,1160,1260],{"id":173,"data":174,"type":35,"maxContentLevel":19,"version":35,"reviews":177,"parsed":1036},{"data":1037,"body":1039,"toc":1065},{"title":765,"description":1038},"Building upon our understanding of DNA, we now turn our attention to genes, the specific sequences of DNA that carry the instructions for building and maintaining an organism.",{"type":768,"children":1040},[1041,1045,1050,1055,1060],{"type":771,"tag":772,"props":1042,"children":1043},{},[1044],{"type":776,"value":1038},{"type":771,"tag":772,"props":1046,"children":1047},{},[1048],{"type":776,"value":1049},"A gene is a segment of DNA that contains the necessary information to produce a functional product, typically a protein.",{"type":771,"tag":772,"props":1051,"children":1052},{},[1053],{"type":776,"value":1054},"Proteins, as we know, are important molecules that perform a wide range of functions in the body, from building tissues to regulating processes in cells.",{"type":771,"tag":772,"props":1056,"children":1057},{},[1058],{"type":776,"value":1059},"The most common range for the length of a human gene is typically between 3,000 to 100,000 base pairs, though genes can vary greatly in size.",{"type":771,"tag":772,"props":1061,"children":1062},{},[1063],{"type":776,"value":1064},"Some genes are as short as a few hundred base pairs, while others can span millions of base pairs.",{"title":765,"searchDepth":25,"depth":25,"links":1066},[],{"id":211,"data":212,"type":35,"maxContentLevel":19,"version":35,"reviews":215,"parsed":1068},{"data":1069,"body":1071,"toc":1158},{"title":765,"description":1070},"The structure of a gene is complex, encompassing more than just a straightforward sequence of nucleotides.",{"type":768,"children":1072},[1073,1084,1096,1107,1115,1120,1132,1143,1148,1153],{"type":771,"tag":772,"props":1074,"children":1075},{},[1076,1078,1083],{"type":776,"value":1077},"The structure of a gene is complex, encompassing more than just a straightforward sequence of ",{"type":771,"tag":783,"props":1079,"children":1080},{},[1081],{"type":776,"value":1082},"nucleotides",{"type":776,"value":848},{"type":771,"tag":772,"props":1085,"children":1086},{},[1087,1089,1094],{"type":776,"value":1088},"A gene is partially made up of coding regions called ",{"type":771,"tag":783,"props":1090,"children":1091},{},[1092],{"type":776,"value":1093},"exons",{"type":776,"value":1095},", which contain the instructions for making proteins.",{"type":771,"tag":772,"props":1097,"children":1098},{},[1099,1101,1105],{"type":776,"value":1100},"These ",{"type":771,"tag":783,"props":1102,"children":1103},{},[1104],{"type":776,"value":1093},{"type":776,"value":1106}," are transcribed into RNA and ultimately translated into proteins, playing a direct role in determining the traits of an organism.",{"type":771,"tag":772,"props":1108,"children":1109},{},[1110],{"type":771,"tag":798,"props":1111,"children":1114},{"alt":800,"src":1112,"title":1113},"image://ba6630d3-ec2f-4bc3-b384-0e586fcfd8e6","Haploid human genome sequence by NHS National Genetics and Genomics Education Centre (CC BY 2.0) \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":1116,"children":1117},{},[1118],{"type":776,"value":1119},"It's also important to note that despite the vast size of the human genome, only about 2% of our DNA actually codes for proteins. The remaining 98% includes non-coding regions, and some elements of these regions are still not fully understood.",{"type":771,"tag":772,"props":1121,"children":1122},{},[1123,1125,1130],{"type":776,"value":1124},"Non-coding regions of genes are known as ‘",{"type":771,"tag":783,"props":1126,"children":1127},{},[1128],{"type":776,"value":1129},"introns",{"type":776,"value":1131},"’, and they appear interspersed between exons.",{"type":771,"tag":772,"props":1133,"children":1134},{},[1135,1137,1141],{"type":776,"value":1136},"Although ",{"type":771,"tag":783,"props":1138,"children":1139},{},[1140],{"type":776,"value":1129},{"type":776,"value":1142}," are transcribed into RNA, they are removed before the RNA is translated into a protein, and the exons are spliced together.",{"type":771,"tag":772,"props":1144,"children":1145},{},[1146],{"type":776,"value":1147},"This splicing actually serves an important purpose, because this splicing of exons doesn’t always have to occur in the same way.",{"type":771,"tag":772,"props":1149,"children":1150},{},[1151],{"type":776,"value":1152},"Different combinations of exons can be spliced together in different ways, leading to the production of different proteins from the same gene.",{"type":771,"tag":772,"props":1154,"children":1155},{},[1156],{"type":776,"value":1157},"This ability to create multiple proteins from a single gene significantly increases the variety of proteins your body can produce, which is important for the complexity and adaptability of living organisms​",{"title":765,"searchDepth":25,"depth":25,"links":1159},[],{"id":245,"data":246,"type":35,"maxContentLevel":19,"version":35,"reviews":249,"parsed":1161},{"data":1162,"body":1164,"toc":1258},{"title":765,"description":1163},"Non-coding regions of genes are not just \"junk DNA\": they include regulatory sequences that control the expression of these coding regions.",{"type":768,"children":1165},[1166,1183,1195,1200,1224,1233,1243,1253],{"type":771,"tag":772,"props":1167,"children":1168},{},[1169,1174,1176,1181],{"type":771,"tag":783,"props":1170,"children":1171},{},[1172],{"type":776,"value":1173},"Non-coding",{"type":776,"value":1175}," regions of genes are not just \"junk DNA\": they include ",{"type":771,"tag":783,"props":1177,"children":1178},{},[1179],{"type":776,"value":1180},"regulatory",{"type":776,"value":1182}," sequences that control the expression of these coding regions.",{"type":771,"tag":772,"props":1184,"children":1185},{},[1186,1188,1193],{"type":776,"value":1187},"By ‘",{"type":771,"tag":783,"props":1189,"children":1190},{},[1191],{"type":776,"value":1192},"gene expression",{"type":776,"value":1194},"’, we mean the process by which the information in a gene is used to create a functional product, like a protein. We’ll come back to this in the following orb.",{"type":771,"tag":772,"props":1196,"children":1197},{},[1198],{"type":776,"value":1199},"These regulatory sequences act like switches, determining when, where, and how much of a particular protein is produced.",{"type":771,"tag":772,"props":1201,"children":1202},{},[1203,1208,1210,1215,1217,1222],{"type":771,"tag":783,"props":1204,"children":1205},{},[1206],{"type":776,"value":1207},"Promoters",{"type":776,"value":1209},", ",{"type":771,"tag":783,"props":1211,"children":1212},{},[1213],{"type":776,"value":1214},"enhancers",{"type":776,"value":1216},", and ",{"type":771,"tag":783,"props":1218,"children":1219},{},[1220],{"type":776,"value":1221},"silencers",{"type":776,"value":1223}," are specific DNA regulatory sequences that act as binding sites for proteins known as transcription factors. These transcription factors either promote or inhibit the transcription of the gene into RNA, depending on the needs of the cell.",{"type":771,"tag":772,"props":1225,"children":1226},{},[1227,1231],{"type":771,"tag":783,"props":1228,"children":1229},{},[1230],{"type":776,"value":1207},{"type":776,"value":1232}," are like starting points, signaling where transcription should begin.",{"type":771,"tag":772,"props":1234,"children":1235},{},[1236,1241],{"type":771,"tag":783,"props":1237,"children":1238},{},[1239],{"type":776,"value":1240},"Enhancers",{"type":776,"value":1242}," are sequences that boost the activity of promoters, increasing gene expression.",{"type":771,"tag":772,"props":1244,"children":1245},{},[1246,1251],{"type":771,"tag":783,"props":1247,"children":1248},{},[1249],{"type":776,"value":1250},"Silencers",{"type":776,"value":1252}," do the opposite—they decrease gene expression.",{"type":771,"tag":772,"props":1254,"children":1255},{},[1256],{"type":776,"value":1257},"This regulation ensures that genes are expressed at the right time and in the right cells, contributing to the proper development and function of an organism.",{"title":765,"searchDepth":25,"depth":25,"links":1259},[],{"id":286,"data":287,"type":35,"maxContentLevel":19,"version":35,"reviews":290,"parsed":1261},{"data":1262,"body":1264,"toc":1302},{"title":765,"description":1263},"Genes are not isolated entities; they interact with each other and with various molecular pathways to influence an organism’s phenotype, the set of observable traits.",{"type":768,"children":1265},[1266,1270,1279,1284,1289,1297],{"type":771,"tag":772,"props":1267,"children":1268},{},[1269],{"type":776,"value":1263},{"type":771,"tag":772,"props":1271,"children":1272},{},[1273,1277],{"type":771,"tag":783,"props":1274,"children":1275},{},[1276],{"type":776,"value":305},{"type":776,"value":1278}," includes everything from eye color to blood type—traits that you can see or measure.",{"type":771,"tag":772,"props":1280,"children":1281},{},[1282],{"type":776,"value":1283},"This interaction between genes and the environment also plays a crucial role in how traits are expressed.",{"type":771,"tag":772,"props":1285,"children":1286},{},[1287],{"type":776,"value":1288},"Mutations in genes, whether spontaneous or induced by external factors, can lead to variations in these traits.",{"type":771,"tag":772,"props":1290,"children":1291},{},[1292],{"type":771,"tag":798,"props":1293,"children":1296},{"alt":800,"src":1294,"title":1295},"image://4120a6de-7c66-4ac8-885f-792584e8abc9","Darwin Hybrid Tulip Mutation 2014-05-01 by LepoRello (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":1298,"children":1299},{},[1300],{"type":776,"value":1301},"Some mutations may have no effect, others can lead to genetic disorders, and some might even confer advantages that contribute to evolutionary change. Genetic disorders are diseases or conditions caused by alterations in the DNA.",{"title":765,"searchDepth":25,"depth":25,"links":1303},[],{"id":331,"data":332,"type":25,"version":35,"maxContentLevel":19,"summaryPage":334,"introPage":342,"pages":1305},[1306,1375,1425,1467],{"id":350,"data":351,"type":35,"maxContentLevel":19,"version":35,"reviews":354,"parsed":1307},{"data":1308,"body":1310,"toc":1373},{"title":765,"description":1309},"Having explored the structure and function of genes, the next step in understanding how genetic information is organized and transmitted is to look at chromosomes.",{"type":768,"children":1311},[1312,1323,1338,1346,1351,1356,1368],{"type":771,"tag":772,"props":1313,"children":1314},{},[1315,1317,1322],{"type":776,"value":1316},"Having explored the structure and function of genes, the next step in understanding how genetic information is organized and transmitted is to look at ",{"type":771,"tag":783,"props":1318,"children":1319},{},[1320],{"type":776,"value":1321},"chromosomes",{"type":776,"value":848},{"type":771,"tag":772,"props":1324,"children":1325},{},[1326,1330,1332,1336],{"type":771,"tag":783,"props":1327,"children":1328},{},[1329],{"type":776,"value":156},{"type":776,"value":1331},", which carry the instructions for building and maintaining an organism, are not scattered randomly within the cell but are instead meticulously organized into structures called ",{"type":771,"tag":783,"props":1333,"children":1334},{},[1335],{"type":776,"value":1321},{"type":776,"value":1337},". This organization ensures that the vast amount of genetic information in our cells is both compactly stored and efficiently accessible.",{"type":771,"tag":772,"props":1339,"children":1340},{},[1341],{"type":771,"tag":798,"props":1342,"children":1345},{"alt":800,"src":1343,"title":1344},"image://a0f79f03-b0ae-4c06-abe1-fed216275394","Pairs of human chromosomes. (Public domain), via Wikimedia Commons",[],{"type":771,"tag":772,"props":1347,"children":1348},{},[1349],{"type":776,"value":1350},"Chromosomes are thread-like structures located in the nucleus of each cell, composed of tightly wound DNA.",{"type":771,"tag":772,"props":1352,"children":1353},{},[1354],{"type":776,"value":1355},"If you think of genes as individual recipes in a vast cookbook, then chromosomes are like the chapters that organize these recipes into manageable sections.",{"type":771,"tag":772,"props":1357,"children":1358},{},[1359,1361,1366],{"type":776,"value":1360},"In humans, the DNA contained within chromosomes is organized into ",{"type":771,"tag":783,"props":1362,"children":1363},{},[1364],{"type":776,"value":1365},"23 pairs",{"type":776,"value":1367},", totaling 46 chromosomes. Each chromosome within a pair is inherited from one parent, so you receive 23 chromosomes from your mother and 23 from your father.",{"type":771,"tag":772,"props":1369,"children":1370},{},[1371],{"type":776,"value":1372},"This pairing ensures that offspring have a combination of genetic material from both parents, which is the foundation of biological diversity.",{"title":765,"searchDepth":25,"depth":25,"links":1374},[],{"id":375,"data":376,"type":35,"maxContentLevel":19,"version":35,"reviews":379,"parsed":1376},{"data":1377,"body":1379,"toc":1423},{"title":765,"description":1378},"Each chromosome contains a long, continuous molecule of DNA, which is tightly coiled and condensed with the help of histones.",{"type":768,"children":1380},[1381,1392,1397,1415],{"type":771,"tag":772,"props":1382,"children":1383},{},[1384,1386,1391],{"type":776,"value":1385},"Each chromosome contains a long, continuous molecule of DNA, which is tightly coiled and condensed with the help of ",{"type":771,"tag":783,"props":1387,"children":1388},{},[1389],{"type":776,"value":1390},"histones",{"type":776,"value":848},{"type":771,"tag":772,"props":1393,"children":1394},{},[1395],{"type":776,"value":1396},"This compact structure allows the long DNA molecules to fit within the confined space of the cell nucleus. Think of it as packing a long, delicate piece of thread into a small spool to keep it organized and protected.",{"type":771,"tag":772,"props":1398,"children":1399},{},[1400,1402,1406,1408,1413],{"type":776,"value":1401},"The DNA is wrapped around ",{"type":771,"tag":783,"props":1403,"children":1404},{},[1405],{"type":776,"value":1390},{"type":776,"value":1407}," to form ",{"type":771,"tag":783,"props":1409,"children":1410},{},[1411],{"type":776,"value":1412},"nucleosomes",{"type":776,"value":1414},", which further coil and fold to create the compact structure of a chromosome.",{"type":771,"tag":772,"props":1416,"children":1417},{},[1418],{"type":771,"tag":798,"props":1419,"children":1422},{"alt":800,"src":1420,"title":1421},"image://1f09ebc7-a5a6-4339-b1ad-e856d14f3a12","Chromatin and histones (Public domain), via Wikimedia Commons",[],{"title":765,"searchDepth":25,"depth":25,"links":1424},[],{"id":427,"data":428,"type":35,"maxContentLevel":19,"version":35,"reviews":431,"parsed":1426},{"data":1427,"body":1429,"toc":1465},{"title":765,"description":1428},"The genes on each chromosome are arranged in a specific order, and their position on a chromosome is referred to as a locus.",{"type":768,"children":1430},[1431,1442,1447,1452,1457],{"type":771,"tag":772,"props":1432,"children":1433},{},[1434,1436,1441],{"type":776,"value":1435},"The genes on each chromosome are arranged in a specific order, and their position on a chromosome is referred to as a ",{"type":771,"tag":783,"props":1437,"children":1438},{},[1439],{"type":776,"value":1440},"locus",{"type":776,"value":848},{"type":771,"tag":772,"props":1443,"children":1444},{},[1445],{"type":776,"value":1446},"This order is consistent across individuals of the same species, which is why scientists can map genes to specific locations on specific chromosomes.",{"type":771,"tag":772,"props":1448,"children":1449},{},[1450],{"type":776,"value":1451},"For example, if a gene responsible for a particular trait is located near the tip of chromosome 4, it will be found in the same place in every human.",{"type":771,"tag":772,"props":1453,"children":1454},{},[1455],{"type":776,"value":1456},"This consistency allows scientists to precisely identify and study the genetic basis of various traits.",{"type":771,"tag":772,"props":1458,"children":1459},{},[1460],{"type":771,"tag":798,"props":1461,"children":1464},{"alt":800,"src":1462,"title":1463},"image://8f1da74f-563c-4a75-9e38-8f3606b983a2","Disease Gene Mapping with Multiple Chromosomes. Image by Esherma1 (CC BY-SA 3.0) \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons",[],{"title":765,"searchDepth":25,"depth":25,"links":1466},[],{"id":455,"data":456,"type":35,"maxContentLevel":19,"version":35,"reviews":459,"parsed":1468},{"data":1469,"body":1471,"toc":1543},{"title":765,"description":1470},"Chromosomes also contain regions that do not code for proteins but are essential for maintaining chromosome integrity and regulating gene expression.",{"type":768,"children":1472},[1473,1477,1485,1494,1503,1515,1520,1531],{"type":771,"tag":772,"props":1474,"children":1475},{},[1476],{"type":776,"value":1470},{"type":771,"tag":772,"props":1478,"children":1479},{},[1480],{"type":771,"tag":798,"props":1481,"children":1484},{"alt":800,"src":1482,"title":1483},"image://097cc366-61e2-4a9c-9124-8313cc55696b","Telomeres by AJC1 (CC BY-SA 4.0) \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia 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occurs, reducing the chromosome number by half so that when fertilization happens, the resulting zygote has the correct number of chromosomes—restoring the full set of 46 in humans.",{"title":765,"searchDepth":25,"depth":25,"links":1544},[],{"id":496,"data":497,"type":25,"version":499,"maxContentLevel":19,"summaryPage":500,"introPage":508,"pages":1546},[1547,1592,1660,1734,1786],{"id":516,"data":517,"type":35,"maxContentLevel":19,"version":19,"reviews":520,"parsed":1548},{"data":1549,"body":1551,"toc":1590},{"title":765,"description":1550},"Gene expression is the process by which the information encoded in DNA is used to produce the observable traits of an organism.",{"type":768,"children":1552},[1553,1562,1567,1572,1582],{"type":771,"tag":772,"props":1554,"children":1555},{},[1556,1560],{"type":771,"tag":783,"props":1557,"children":1558},{},[1559],{"type":776,"value":260},{"type":776,"value":1561}," is the process by which the information encoded in DNA is used to produce the observable traits of an organism.",{"type":771,"tag":772,"props":1563,"children":1564},{},[1565],{"type":776,"value":1566},"This concept is central to understanding how the instructions in our genes are translated into the proteins that perform almost every function in the body.",{"type":771,"tag":772,"props":1568,"children":1569},{},[1570],{"type":776,"value":1571},"To grasp gene expression, we need to start with the central dogma of molecular biology, which outlines the flow of genetic information from DNA to RNA to protein.",{"type":771,"tag":772,"props":1573,"children":1574},{},[1575,1577],{"type":776,"value":1576},"The process begins with transcription, where the ",{"type":771,"tag":783,"props":1578,"children":1579},{},[1580],{"type":776,"value":1581},"DNA sequence of a gene is copied into messenger RNA (mRNA).",{"type":771,"tag":772,"props":1583,"children":1584},{},[1585],{"type":771,"tag":798,"props":1586,"children":1589},{"alt":800,"src":1587,"title":1588},"image://fbdd9aec-178b-42f8-9435-ad0efa4c4f4b","TranscriptionGraphic PublicDomain (CC0) \u003Chttp://creativecommons.org/publicdomain/zero/1.0/deed.en>, via Wikimedia Commons",[],{"title":765,"searchDepth":25,"depth":25,"links":1591},[],{"id":537,"data":538,"type":35,"maxContentLevel":19,"version":35,"reviews":541,"parsed":1593},{"data":1594,"body":1596,"toc":1658},{"title":765,"description":1595},"Imagine DNA as a large cookbook, and each gene as a specific recipe within it.",{"type":768,"children":1597},[1598,1602,1631,1640,1648,1653],{"type":771,"tag":772,"props":1599,"children":1600},{},[1601],{"type":776,"value":1595},{"type":771,"tag":772,"props":1603,"children":1604},{},[1605,1609,1611,1615,1618,1622,1624,1629],{"type":771,"tag":783,"props":1606,"children":1607},{},[1608],{"type":776,"value":65},{"type":776,"value":1610}," is like copying one of these recipes onto a separate sheet of paper—this sheet is the mRNA, which will carry the instructions out of the DNA “cookbook” and into the cell’s kitchen.",{"type":771,"tag":1612,"props":1613,"children":1614},"br",{},[],{"type":771,"tag":1612,"props":1616,"children":1617},{},[],{"type":771,"tag":783,"props":1619,"children":1620},{},[1621],{"type":776,"value":65},{"type":776,"value":1623}," is initiated when an enzyme called ",{"type":771,"tag":783,"props":1625,"children":1626},{},[1627],{"type":776,"value":1628},"RNA polymerase",{"type":776,"value":1630}," binds to a specific region of the DNA, known as the promoter, which signals the start of the gene.",{"type":771,"tag":772,"props":1632,"children":1633},{},[1634,1638],{"type":771,"tag":783,"props":1635,"children":1636},{},[1637],{"type":776,"value":1628},{"type":776,"value":1639}," unwinds the DNA helix and creates a complementary strand of mRNA by matching RNA nucleotides to the DNA template.",{"type":771,"tag":772,"props":1641,"children":1642},{},[1643],{"type":771,"tag":798,"props":1644,"children":1647},{"alt":800,"src":1645,"title":1646},"image://c8f713a4-6965-43b6-ab48-93f908ab5427","Image: Genomics Education Programme, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":1649,"children":1650},{},[1651],{"type":776,"value":1652},"Unlike DNA, where adenine (A) pairs with thymine (T), in RNA, adenine pairs with uracil (U).",{"type":771,"tag":772,"props":1654,"children":1655},{},[1656],{"type":776,"value":1657},"This newly formed mRNA strand is like a portable recipe, ready to be used outside the nucleus of the cell.",{"title":765,"searchDepth":25,"depth":25,"links":1659},[],{"id":556,"data":557,"type":35,"maxContentLevel":19,"version":25,"reviews":560,"parsed":1661},{"data":1662,"body":1664,"toc":1732},{"title":765,"description":1663},"After transcription, once the mRNA is synthesized, it undergoes processing. This involves removing introns—non-coding sections of RNA—and splicing together exons, the coding regions that will be used to build the protein.",{"type":768,"children":1665},[1666,1690,1698,1709,1714],{"type":771,"tag":772,"props":1667,"children":1668},{},[1669,1671,1676,1678,1682,1684,1688],{"type":776,"value":1670},"After transcription, once the mRNA is synthesized, it undergoes ",{"type":771,"tag":783,"props":1672,"children":1673},{},[1674],{"type":776,"value":1675},"processing",{"type":776,"value":1677},". This involves removing ",{"type":771,"tag":783,"props":1679,"children":1680},{},[1681],{"type":776,"value":1129},{"type":776,"value":1683},"—non-coding sections of RNA—and splicing together ",{"type":771,"tag":783,"props":1685,"children":1686},{},[1687],{"type":776,"value":1093},{"type":776,"value":1689},", the coding regions that will be used to build the protein.",{"type":771,"tag":772,"props":1691,"children":1692},{},[1693],{"type":771,"tag":798,"props":1694,"children":1697},{"alt":800,"src":1695,"title":1696},"image://ff400c8d-f1f1-4ecb-8227-80e95384a618","DNA exons and introns splicing process. Image (Public domain), via Wikimedia Commons",[],{"type":771,"tag":772,"props":1699,"children":1700},{},[1701,1703,1708],{"type":776,"value":1702},"The processed mRNA then exits the nucleus and enters the cytoplasm, where it meets the cell's ",{"type":771,"tag":783,"props":1704,"children":1705},{},[1706],{"type":776,"value":1707},"ribosomes",{"type":776,"value":848},{"type":771,"tag":772,"props":1710,"children":1711},{},[1712],{"type":776,"value":1713},"Think of ribosomes as chefs in the cell’s kitchen, responsible for reading the mRNA \"recipe\" and assembling the protein.",{"type":771,"tag":772,"props":1715,"children":1716},{},[1717,1719,1724,1726,1730],{"type":776,"value":1718},"In the ",{"type":771,"tag":783,"props":1720,"children":1721},{},[1722],{"type":776,"value":1723},"translation",{"type":776,"value":1725}," stage, the ribosome reads the mRNA sequence and translates it into a chain of ",{"type":771,"tag":783,"props":1727,"children":1728},{},[1729],{"type":776,"value":587},{"type":776,"value":1731},", the building blocks of proteins.",{"title":765,"searchDepth":25,"depth":25,"links":1733},[],{"id":576,"data":577,"type":35,"maxContentLevel":19,"version":35,"reviews":580,"parsed":1735},{"data":1736,"body":1738,"toc":1784},{"title":765,"description":1737},"During translation, transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together in a particular order.",{"type":768,"children":1739},[1740,1750,1761,1769,1779],{"type":771,"tag":772,"props":1741,"children":1742},{},[1743,1744,1748],{"type":776,"value":1507},{"type":771,"tag":783,"props":1745,"children":1746},{},[1747],{"type":776,"value":1723},{"type":776,"value":1749},", transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are linked together in a particular order.",{"type":771,"tag":772,"props":1751,"children":1752},{},[1753,1754,1759],{"type":776,"value":886},{"type":771,"tag":783,"props":1755,"children":1756},{},[1757],{"type":776,"value":1758},"Transfer RNA",{"type":776,"value":1760}," (tRNA) molecules know the correct order in which to bring amino acids to the ribosome because they follow the sequence of codons in the mRNA.",{"type":771,"tag":772,"props":1762,"children":1763},{},[1764],{"type":771,"tag":798,"props":1765,"children":1768},{"alt":800,"src":1766,"title":1767},"image://2c1750c3-690b-43a5-88cd-eb11a0398229","Transcription and translation. Image: NHS National Genetics and Genomics Education Centre, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":1770,"children":1771},{},[1772,1777],{"type":771,"tag":783,"props":1773,"children":1774},{},[1775],{"type":776,"value":1776},"Codons",{"type":776,"value":1778}," are groups of three nucleotides in the mRNA that specify which amino acid should be added next.",{"type":771,"tag":772,"props":1780,"children":1781},{},[1782],{"type":776,"value":1783},"The growing chain of amino acids eventually folds into a functional protein, ready to carry out its role in the cell.",{"title":765,"searchDepth":25,"depth":25,"links":1785},[],{"id":589,"data":590,"type":35,"maxContentLevel":19,"version":35,"reviews":593,"parsed":1787},{"data":1788,"body":1790,"toc":1841},{"title":765,"description":1789},"Gene expression is one-way directed process, though not a simple one; it is carefully regulated at multiple stages to ensure that proteins are produced at the right time, in the right place, and in the right amounts.",{"type":768,"children":1791},[1792,1801,1806,1816,1824,1836],{"type":771,"tag":772,"props":1793,"children":1794},{},[1795,1799],{"type":771,"tag":783,"props":1796,"children":1797},{},[1798],{"type":776,"value":260},{"type":776,"value":1800}," is one-way directed process, though not a simple one; it is carefully regulated at multiple stages to ensure that proteins are produced at the right time, in the right place, and in the right amounts.",{"type":771,"tag":772,"props":1802,"children":1803},{},[1804],{"type":776,"value":1805},"Additionally, other mechanisms like regulatory RNAs and epigenetic modifications can fine-tune the expression of genes in response to the cell’s needs or environmental changes.",{"type":771,"tag":772,"props":1807,"children":1808},{},[1809,1814],{"type":771,"tag":783,"props":1810,"children":1811},{},[1812],{"type":776,"value":1813},"Epigenetic modifications",{"type":776,"value":1815}," involve changes that affect gene expression without altering the DNA sequence itself. A common example is the addition of a chemical group called a methyl group to DNA, which can turn a gene off or reduce its activity.",{"type":771,"tag":772,"props":1817,"children":1818},{},[1819],{"type":771,"tag":798,"props":1820,"children":1823},{"alt":800,"src":1821,"title":1822},"image://01b6b043-348d-4e99-97c5-663c832b0b67","Epigenetic mechanisms (Public domain), via Wikimedia Commons",[],{"type":771,"tag":772,"props":1825,"children":1826},{},[1827,1829,1834],{"type":776,"value":1828},"For example, in response to chronic stress, ",{"type":771,"tag":783,"props":1830,"children":1831},{},[1832],{"type":776,"value":1833},"methyl groups",{"type":776,"value":1835}," may be added to genes involved in stress regulation, lowering their activity. This could be the body's way of adapting to prolonged stress by lessening the impact of stress hormones.",{"type":771,"tag":772,"props":1837,"children":1838},{},[1839],{"type":776,"value":1840},"This tightly regulated process of gene expression is also the foundation of many modern biotechnologies, such as genetic engineering and gene therapy, which aim to manipulate gene expression to treat genetic disorders by restoring the proper levels of key proteins.",{"title":765,"searchDepth":25,"depth":25,"links":1842},[],{"id":619,"data":620,"type":25,"version":35,"maxContentLevel":19,"summaryPage":621,"introPage":629,"pages":1844},[1845,1923,2026,2098],{"id":637,"data":638,"type":35,"maxContentLevel":19,"version":35,"reviews":641,"parsed":1846},{"data":1847,"body":1849,"toc":1921},{"title":765,"description":1848},"With a solid understanding of how genes are organized into chromosomes and how they function within cells, we can now explore how these genes are passed from one generation to the next—a process known as heredity.",{"type":768,"children":1850},[1851,1862,1867,1879,1887,1897,1905,1916],{"type":771,"tag":772,"props":1852,"children":1853},{},[1854,1856,1861],{"type":776,"value":1855},"With a solid understanding of how genes are organized into chromosomes and how they function within cells, we can now explore how these genes are passed from one generation to the next—a process known as ",{"type":771,"tag":783,"props":1857,"children":1858},{},[1859],{"type":776,"value":1860},"heredity",{"type":776,"value":848},{"type":771,"tag":772,"props":1863,"children":1864},{},[1865],{"type":776,"value":1866},"Heredity is the mechanism by which genetic information is transmitted from parents to offspring, ensuring the continuity of life and the preservation of traits within a species.",{"type":771,"tag":772,"props":1868,"children":1869},{},[1870,1872,1877],{"type":776,"value":1871},"The foundational principles of heredity were first uncovered by ",{"type":771,"tag":783,"props":1873,"children":1874},{},[1875],{"type":776,"value":1876},"Gregor Mendel",{"type":776,"value":1878},", a 19th-century scientist often referred to as the \"father of modern genetics.\"",{"type":771,"tag":772,"props":1880,"children":1881},{},[1882],{"type":771,"tag":798,"props":1883,"children":1886},{"alt":800,"src":1884,"title":1885},"image://c936a398-f78c-43cf-973a-da6657216bb6","Gregor Mendel (Public domain), via Wikimedia Commons",[],{"type":771,"tag":772,"props":1888,"children":1889},{},[1890,1895],{"type":771,"tag":783,"props":1891,"children":1892},{},[1893],{"type":776,"value":1894},"Mendel",{"type":776,"value":1896}," discovered these patterns through meticulous experiments with pea plants, Mendel discovered that traits are inherited in specific, predictable patterns, governed by what we now understand to be genes.",{"type":771,"tag":772,"props":1898,"children":1899},{},[1900],{"type":771,"tag":798,"props":1901,"children":1904},{"alt":800,"src":1902,"title":1903},"image://d6b8eb67-9a35-4191-8080-86b82ddc6fad","Doperwt rijserwt peulen Pisum sativum by Rasbak (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":1906,"children":1907},{},[1908,1909,1914],{"type":776,"value":1100},{"type":771,"tag":783,"props":1910,"children":1911},{},[1912],{"type":776,"value":1913},"laws of heredity",{"type":776,"value":1915}," laid the groundwork for modern genetics by establishing the idea that genes are the fundamental units of inheritance, passed from parents to offspring in a predictable manner.",{"type":771,"tag":772,"props":1917,"children":1918},{},[1919],{"type":776,"value":1920},"The discovery of chromosomes as the carriers of genes later confirmed and expanded on Mendel’s principles, integrating them into the broader framework of molecular biology.",{"title":765,"searchDepth":25,"depth":25,"links":1922},[],{"id":654,"data":655,"type":35,"maxContentLevel":19,"version":35,"reviews":658,"parsed":1924},{"data":1925,"body":1927,"toc":2024},{"title":765,"description":1926},"One of Mendel’s key discoveries was the concept that genes exist in pairs, with each parent contributing one 'version' of that gene to their offspring. These pairs of genes are known as alleles, and they can be either dominant or recessive.",{"type":768,"children":1928},[1929,1954,1965,1977,1995,2003,2014,2019],{"type":771,"tag":772,"props":1930,"children":1931},{},[1932,1934,1939,1941,1946,1948,1953],{"type":776,"value":1933},"One of Mendel’s key discoveries was the concept that ",{"type":771,"tag":783,"props":1935,"children":1936},{},[1937],{"type":776,"value":1938},"genes exist in pairs",{"type":776,"value":1940},", with each parent contributing one 'version' of that gene to their offspring. These pairs of genes are known as alleles, and they can be either ",{"type":771,"tag":783,"props":1942,"children":1943},{},[1944],{"type":776,"value":1945},"dominant",{"type":776,"value":1947}," or ",{"type":771,"tag":783,"props":1949,"children":1950},{},[1951],{"type":776,"value":1952},"recessive",{"type":776,"value":848},{"type":771,"tag":772,"props":1955,"children":1956},{},[1957,1959,1964],{"type":776,"value":1958},"This principle is known as Mendel’s ",{"type":771,"tag":783,"props":1960,"children":1961},{},[1962],{"type":776,"value":1963},"Third Law of Dominance",{"type":776,"value":848},{"type":771,"tag":772,"props":1966,"children":1967},{},[1968,1970,1975],{"type":776,"value":1969},"A ",{"type":771,"tag":783,"props":1971,"children":1972},{},[1973],{"type":776,"value":1974},"dominant allele",{"type":776,"value":1976}," is like the louder voice in a pair—it tends to express itself in the organism’s traits, even if the other allele (from the other parent) is different.",{"type":771,"tag":772,"props":1978,"children":1979},{},[1980,1982,1987,1989,1993],{"type":776,"value":1981},"For instance, if the allele for ",{"type":771,"tag":783,"props":1983,"children":1984},{},[1985],{"type":776,"value":1986},"purple flower",{"type":776,"value":1988}," color is ",{"type":771,"tag":783,"props":1990,"children":1991},{},[1992],{"type":776,"value":1945},{"type":776,"value":1994},", a pea plant with one purple flower allele and one white flower allele will still have purple flowers because the dominant purple allele \"masks\" the presence of the recessive white allele.",{"type":771,"tag":772,"props":1996,"children":1997},{},[1998],{"type":771,"tag":798,"props":1999,"children":2002},{"alt":800,"src":2000,"title":2001},"image://2a58dca5-8ff6-402c-8d30-1ad3f04d72fe","Pisum sativum biflorum1 (Public domain), via Wikimedia Commons",[],{"type":771,"tag":772,"props":2004,"children":2005},{},[2006,2007,2012],{"type":776,"value":1969},{"type":771,"tag":783,"props":2008,"children":2009},{},[2010],{"type":776,"value":2011},"recessive allele",{"type":776,"value":2013}," is quieter and will only express itself in the organism’s traits if both alleles for that trait are recessive.",{"type":771,"tag":772,"props":2015,"children":2016},{},[2017],{"type":776,"value":2018},"In our example, the white flower color would only appear if the pea plant inherited the white allele from both parents. But if it appeared alongside a dominant purple the white allele would remain hidden, but could still be passed on to the next generation.",{"type":771,"tag":772,"props":2020,"children":2021},{},[2022],{"type":776,"value":2023},"So, if a pea plant carries one allele for purple flowers (dominant) and one for white flowers (recessive), the dominant purple allele will determine the flower color, while the white allele remains hidden but can still be passed on to the next generation.",{"title":765,"searchDepth":25,"depth":25,"links":2025},[],{"id":691,"data":692,"type":35,"maxContentLevel":19,"version":35,"reviews":695,"parsed":2027},{"data":2028,"body":2030,"toc":2096},{"title":765,"description":2029},"Mendel’s first law, the Law of Segregation, explains how these alleles are separated during the formation of gametes—sperm and egg cells—so that each gamete carries only one allele for each trait.",{"type":768,"children":2031},[2032,2044,2049,2057,2069,2081,2086,2091],{"type":771,"tag":772,"props":2033,"children":2034},{},[2035,2037,2042],{"type":776,"value":2036},"Mendel’s first law, ",{"type":771,"tag":783,"props":2038,"children":2039},{},[2040],{"type":776,"value":2041},"the Law of Segregation",{"type":776,"value":2043},", explains how these alleles are separated during the formation of gametes—sperm and egg cells—so that each gamete carries only one allele for each trait.",{"type":771,"tag":772,"props":2045,"children":2046},{},[2047],{"type":776,"value":2048},"When fertilization occurs, the offspring inherits one allele from each parent, restoring the pair.",{"type":771,"tag":772,"props":2050,"children":2051},{},[2052],{"type":771,"tag":798,"props":2053,"children":2056},{"alt":800,"src":2054,"title":2055},"image://f9f29b34-32ad-47d2-ab3b-76da6a380795","Sperm-egg (Public domain), via Wikimedia 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shape).",{"type":771,"tag":772,"props":2087,"children":2088},{},[2089],{"type":776,"value":2090},"This principle applies primarily to genes located on different chromosomes or far apart on the same chromosome.",{"type":771,"tag":772,"props":2092,"children":2093},{},[2094],{"type":776,"value":2095},"Mendel’s experiments showed that when crossing plants with two different traits, the offspring exhibited combinations of traits in ratios that could be mathematically predicted, demonstrating the independent nature of allele assortment.",{"title":765,"searchDepth":25,"depth":25,"links":2097},[],{"id":729,"data":730,"type":35,"maxContentLevel":19,"version":35,"reviews":733,"parsed":2099},{"data":2100,"body":2102,"toc":2182},{"title":765,"description":2101},"As well as introducing the concept of dominant and recessive traits, Mendel’s work laid the foundation for the concepts of genotype and phenotype.",{"type":768,"children":2103},[2104,2122,2132,2142,2150,2155,2160,2165,2170],{"type":771,"tag":772,"props":2105,"children":2106},{},[2107,2109,2114,2116,2121],{"type":776,"value":2108},"As well as introducing the concept of dominant and recessive traits, Mendel’s work laid the foundation for the concepts of ",{"type":771,"tag":783,"props":2110,"children":2111},{},[2112],{"type":776,"value":2113},"genotype",{"type":776,"value":2115}," and ",{"type":771,"tag":783,"props":2117,"children":2118},{},[2119],{"type":776,"value":2120},"phenotype",{"type":776,"value":848},{"type":771,"tag":772,"props":2123,"children":2124},{},[2125,2126,2130],{"type":776,"value":886},{"type":771,"tag":783,"props":2127,"children":2128},{},[2129],{"type":776,"value":2113},{"type":776,"value":2131}," refers to the genetic makeup of an organism—the specific combination of alleles it possesses.",{"type":771,"tag":772,"props":2133,"children":2134},{},[2135,2136,2140],{"type":776,"value":886},{"type":771,"tag":783,"props":2137,"children":2138},{},[2139],{"type":776,"value":2120},{"type":776,"value":2141}," is the observable expression of these traits—what we can actually see, such as eye color or height.",{"type":771,"tag":772,"props":2143,"children":2144},{},[2145],{"type":771,"tag":798,"props":2146,"children":2149},{"alt":800,"src":2147,"title":2148},"image://3da0b941-010c-4139-9ac8-065324b204da","Coquina variation in phenotype. Image by Debivort (CC BY-SA 3.0) \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons",[],{"type":771,"tag":772,"props":2151,"children":2152},{},[2153],{"type":776,"value":2154},"While the genotype determines the potential for a trait, the phenotype can be influenced by interactions between different alleles, as well as environmental factors.",{"type":771,"tag":772,"props":2156,"children":2157},{},[2158],{"type":776,"value":2159},"For example, even if someone has the genetic potential for tall stature (genotype), factors like nutrition during growth years can influence the actual height (phenotype).",{"type":771,"tag":772,"props":2161,"children":2162},{},[2163],{"type":776,"value":2164},"The principles of Mendel’s laws apply universally to all sexually reproducing organisms, from plants to animals to humans.",{"type":771,"tag":772,"props":2166,"children":2167},{},[2168],{"type":776,"value":2169},"They form the basis for understanding not only simple inheritance patterns but also more complex phenomena such as genetic disorders, polygenic traits (traits controlled by multiple genes), and the role of genetic variation in evolution.",{"type":771,"tag":772,"props":2171,"children":2172},{},[2173,2175,2180],{"type":776,"value":2174},"Heredity is the engine of ",{"type":771,"tag":783,"props":2176,"children":2177},{},[2178],{"type":776,"value":2179},"evolution",{"type":776,"value":2181},"—and this will be the topic of our final orb.",{"title":765,"searchDepth":25,"depth":25,"links":2183},[],{"left":4,"top":4,"width":2185,"height":2185,"rotate":4,"vFlip":6,"hFlip":6,"body":2186},24,"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"m9 18l6-6l-6-6\"/>",{"left":4,"top":4,"width":2185,"height":2185,"rotate":4,"vFlip":6,"hFlip":6,"body":2188},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"M4 5h16M4 12h16M4 19h16\"/>",1778179374220]