Bio 30 Unit C Lesson 3

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Biology 30: Unit C Lesson Assignment 3 Crossing Over and Gene Mutations: When Things Don’t Go as Planned Name: /45 Answer by clicking in the line below the question and typing your answer. Please answer in complete sentences. Part One: Gene Mapping and Crossing Over (10 marks) 1. Lab: Mapping Chromosomes Constructing gene maps allows researchers to locate and study genes and their inheritance. You will practise creating your own map by completing Part A of “Thought Lab 17.1” on page 602 of your textbook. Follow the instructions given in the text for Part A. Save your responses to each of the questions and create a simple graphic indicating the distance in map units between the genes studied. Place a copy of each in the answer box below. The mark breakdown is indicated. Procedure Follow the instructions given in the text for Part A. Create a simple graphic indicating the distance in map units between the genes studied. Make sure your map is correct with respect to relative distance. Use a key such as 1 cm = 1 map unit. Insert a picture of your map. Through calculations based on the provided methodology, it was determined that 19.6% of the F1 generation exhibit recombination. This percentage correlates to 19.6 map units. Upon recalculating 96+100×1000% and dividing by 1000, the revised result is 1.096, indicating that approximately 1.096% of the F1 generation display recombination, rather than the previously mentioned 19.6%. Interpreting Recombination Percentage: Bio.30.13Asn © NorthStar Academy 2009 1

This adjusted percentage signifies that a small proportion, roughly 1.096% of the F1 generation are recombinants. It's important to note this adjusted figure as it reflects a more precise estimation of genetic recombination. Relating Percentage to Map Units: Consequently, this recalibration alters the understanding of gene distances. Instead of 19.6 19.6 map units, the genes for eye color and wing type are approximately 1.096 map units apart, showcasing a notably smaller distance than previously indicated. Ensuring accuracy in calculations is critical in gene mapping, as it directly impacts the interpretation of genetic distances between traits. Genetic Map: Eye Color: ------------------- 12.2 map units ------------------> Body Color: <-------------- 7.4 map units -------------------> Wing Type: ------------------------------------------19.6 map units apart ----------------------------------------- /6 Analysis Answer “Analysis” questions 1 and 2. (2 marks each) Question 1 emphasise two potential factors: The percentage of recombinants observed in the F1 generation appears to have a direct correlation with gene distance, for one. Increased linkage due to closer gene proximity also seems to amplify the likelihood of crossing over. These observations, alternatively, could be accounted for by the presence of parental type chromosomes in the offspring. Question 2: The use of this data for mapping human chromosomes may pose challenges because humans have prolonged generational cycles, making it difficult to accurately determine crossover frequencies. Furthermore, due to the polygenic nature of humans, individuals might not easily adhere to directives about their reproductive partner choices; hence rendering this pursuit less relevant. /4 Part Two: Crossing Over (13 marks) Bio.30.13Asn © NorthStar Academy 2009 2

1. AH Sturtevant, a student who worked with Thomas Morgan, hypothesized that  Genes are located in a linear series along a chromosome, much like beads on a string  Genes that are closer together will be separated less frequenctly than those that are far apart  Crossover frequencies can be used to construct gene maps. Sturtevant’s work with Drosophila helped establish techniques for chromosome maps. Procedure Examine the picture of a chromosome (Figure 1). Crossing over takes place when breaks occur in the chromatids of homologous chromosomes during meiosis. The chromatids break and join with the chromatids of homologous chromosomes. This causes an exchange of alleles between chromosomes. Figure 1 a. Circle the areas of the chromatids that show crossing over. /1 Bio.30.13Asn © NorthStar Academy 2009 3

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b. Using the digram above, which genes appear farthest apart? (Choose from EF, FG or EG) EG are the farthest apart. /1 c. Which alleles have been exchanged? G ←> g F←-> f /1 In 1913, Sturtevant used crossover frequencies of Drosophila to construct chromosome maps. To determine map distances, he arbitrarily assigned one recombination for every 100 fertilized eggs. For example, genes that had a crossover frequency of 15% were said to be 15 units apart. Genes that had a 5% recombination rate were much closer. These genes are 5 units apart. d. Using the data in Table 1, determine the distance between genes E and F. Table 1 Distance is 6MU /1 e. Would the distance between genes e and f be identical? Use the data in Table 2 to construct a complete gene map. This does not need to be handed in. It would be identical. Table 2 Bio.30.13Asn © NorthStar Academy 2009 4

f. What is the distance between genes E and G? The distance between genes E and G are 10 MU /1 g. What is the distance between genes F and G? The distance between F and G is 4 MU /1 Analysis h. What mathematical evidence indicates that gene F must be found between genes E and G? The mathematic evidence that indicates Gene F must be found between gene E and G is E-G = 10 Which is the biggest distance F-G = -4 = E-F = 6 /1 2. Use the following information to answer the next 2 questions. In Drosophila, genes for eye colour and wing size are linked. White eyes and miniature wings are recessive to the wild (normal) traits. A cross between white-eyed, miniature winged females and wild-type males, heterozygous for both traits, was done. The phenotypes of the offspring are shown in the table. Bio.30.13Asn © NorthStar Academy 2009 5

a. In the table, the cross over frequency for the two genes is a. 19% b. 32% c. 37% d. 63% /1 b. In the table, the map distance between the two genes is a. 19 units b. 32 units c. 37 units d. 63 units /1 3. The recombination frequency among genes found on the same chromosomes depends on a. whether the genes are dominant or recessive b. the physical distance between the two genes c. the number of genes on the chromosome d. the nature of the phenotypes involved /1 4. Use the following information to answer the next 3 questions. The chromosome map below shows the portion of a chromosome that carries genes for scalloped wings, bar eyes, and garnet eyes: all mutant traits in Drosophila. It was drawn as a result of data from several test crosses. Bio.30.13Asn © NorthStar Academy 2009 6

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bar eye scalloped wing garnet eye 6 units 7 units 512010 a. The chromosome map shows that the cross over frequency between bar eye and garnet eye genes during meiosis is a. 1% b. 6% c. 7% d. 13% /1 b. The chromosome map shows that the cross over frequency between garnet eye and scalloped wing genes during meiosis is a. 1% b. 6% c. 7% d. 13% /1 c. The chromosome map shows that the cross over frequency between scalloped wing and bar eye genes during meiosis is a. 1% b. 6% c. 7% d. 13% /1 Bio.30.13Asn © NorthStar Academy 2009 7

Part Three: Gene Mutations (22 marks) 1. Part 1 Of the 72 700 Canadians who died from cancer in 2007, 19 900 died from lung cancer, the most preventable of all cancers. Examine the graphs in the “Thought Lab 18.3: Investigating Cancer Genes” on page 646. Analysis Answer the “Analysis” Question below. The chemical reactions within cells experience significant impact from personal choices, such as diet, exercise, and environmental factor exposure. The type of food one consumes for instance can sway the availability of nutrients for cellular reactions; similarly through its influence on metabolism and energy production exercise affects these crucial processes. Pollutants or toxins, as environmental factors, can disrupt cellular processes; poor choices may imbalance these reactions and precipitate a range of health issues. Inadequate nutrition exemplifies this: it potentially impairs energy production thus inducing fatigue or compromising immune function. Cellular damage, potentially leading to diseases such as cancer or respiratory issues, could result from environmental toxins. The act of researching molecular reactions related to smoking often uncovers numerous mutagens. A complex mixture of chemicals, known or potential mutagens, is present in each cigarette. The identification process can uncover an extensive number of mutagens despite potential variations in findings across different research studies. Cigarette smoke commonly harbors several dozen, and even hundreds, of diverse mutagens. These substances actively inflict DNA damage: a direct causative factor in mutations that escalate the risk for cancer; they also provoke an array of other health complications their pernicious effects are not limited to a singular ailment. The Canadian Lung Association must employ various engaging mediums, such as social media, interactive online content, and school-based events to effectively communicate the risks of smoking to youth aged 10-15. The approach should pivot around visually impactful messages: use graphics or videos that showcase not only the detrimental effects on lung health but also overall well-being. Key emphasis should be placed on highlighting both social consequences - appearance impact for instance - and physical ones including a hampered athletic performance along with associated health risks like respiratory issues; increased susceptibility towards cancer is another critical point to underscore here. Engaging and relatable content that encourages positive alternatives, while highlighting the benefits of a smoke-free lifestyle, will also crucially resonate with this impressionable audience. Bio.30.13Asn © NorthStar Academy 2009 8

/3 Part 2 Choose one other mutagen (physical or chemical), unrelated to smoking, to research in detail. (Have the mutagen approved by me before you proceed). Answer the following questions about the mutagen.  Where is the mutagen found?  Are there any positive uses for this mutagen?  How does the mutagen cause the change in DNA?  What effect can the mutagen eventually cause?  How can contact with the mutagen be prevented? Do any human activities cuase an increase in contact with the mutagen? Various industrial settings such as petroleum refining, chemical manufacturing, and rubber production harbor the prevalent chemical mutagen: benzene. Vehicle emissions contain it too; furthermore, it constitutes a component of cigarette smoke. Benzene despite its acknowledged detrimental effects proves useful in producing plastics, synthetic fibers, and lubricants. Through metabolic activation in the body, this mutagen exerts its influence; it generates reactive intermediates that bind to DNA. These interactions disrupt replication and repair mechanisms a process which leads inevitably to genetic mutations. Prolonged exposure to Benzene links severely with health consequences: leukemia, blood disorders, bone marrow damage, immune system impairment - even anemia can result. Industries must adhere strictly to safety protocols; protective gear should be worn consistently, and proper ventilation always ensured these are always the preventive measures against Benzene exposure. Minimizing environmental exposure necessitates crucial regulatory control over emissions in industrial processes and automobiles. The significance of stringent safety practices and regulations is underscored by human activities like industrial operations, tobacco smoking, and the use of Benzene-containing products that contribute to heightened exposure. This emphasizes potential health hazards associated with this mutagen, calling for effective mitigation strategies. /10 2. Distinguish between oncogenes and proto-oncogenes. Distinct in their roles within cellular function, proto-oncogenes act as normal genes that regulate cell growth, division, and differentiation. They play essential roles in maintaining cellular functions; however, alteration or mutation can cause a transformation into oncogenes. Proto- oncogenes derive oncogenes: these possess the ability to provoke uncontrolled cell growth and division. Proto-oncogenes, in contrast aids in regular cellular processes; however, activations of mutations or abnormal regulation can transform them into oncogenic variants driving aberrant Bio.30.13Asn © NorthStar Academy 2009 9

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cell proliferation that contributes to cancer development. The change from proto-oncogene state to an outright oncogenic one marks a pivotal transition within cellular behavior shifting from normal functionality towards potential malignant transformation. /2 3. Explain how oncogenes are activated. Various mechanisms activate oncogenes, leading to their abnormal function and subsequently promoting uncontrolled cell growth. Frequently, mutations in proto-oncogenes or regulatory changes cause this activation. Such alterations comprise point mutations, gene amplification, chromosomal translocations; alternatively, they may be alterations in gene expression levels. Changes in the genetic sequence specifically, point mutations result in a hyperactive or constitutively active form of the gene product. Gene amplification, on the other hand, boosts its expression and activity by increasing copies of an oncogene. When DNA segments containing proto-oncogenes break off and reattach to different chromosomes, chromosomal translocations occur; this process often results in abnormal gene fusion proteins. Transcriptional activators or repressors can instigate changes in gene expression regulation, disrupting the normal control mechanisms of proto-oncogenes and activating them. When these alterations occur because of mutations or regulatory shifts, they mutate into oncogenes, fostering uncontrolled cell proliferation that potentially fuels cancer development. /2 4. Clearly define the following terms: mutation, frameshift, mutation, point mutation, nonsense mutation, missense mutation. Any alteration in the DNA sequence is a mutation, and specifically, a frameshift mutation occurs when there are insertions, deletions, or additions of nucleotides. This causes an abrupt shift in the reading frame during translation; this often leads to nonfunctional proteins. On the other hand, point mutations involve changes in single nucleotide base pairs: they can manifest as either nonsense mutations – which introduce premature stop codons – or missense mutations where one amino acid substitutes for another within protein sequences. Protein synthesis prematurely truncates due to nonsense mutations: this leads to nonfunctional proteins. Conversely, missense mutations alter either the structure or function of a protein - directly influencing their role within cells. Whether they alter reading frames or single nucleotides, these mutations can yield diverse consequences on the final protein product; they impact cellular processes and potentially precipitate various genetic disorders or conditions. /5 Bio.30.13Asn © NorthStar Academy 2009 10

Bio 30 Unit C Lesson 3

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