Imagine a population of mice with two alleles A and a at a locus. The initial allele frequencies are A = 0.7 and a = 0.3. a. Enter the initial allele frequencies in the diagram below: Initial allele frequencies: A: 0.7 a: 0.3 Number of zygotes: Final allele frequencies: A: a: AAAa Genotype: Number of juveniles: Number of adults: AAA Genotype: Genotype: b. Complete a Punnett square analysis (next page, left-hand side of diagram) for determining the genotypes of 100 zygotes produced from this gene pool (assume no blind luck). Use Figure 6.6 as a model. c. In the diagram above, construct a bar graph of the expected number of zygotes for each genotype and write the number above each bar (draw the bars approximately to scale). Use Figure 6.8 as a model. d. Assume all zygotes survive and develop into juveniles. Complete the bar graph for the number of juveniles expected in each genotype. Assume all of the juveniles survive to become breeding adults. Complete the bar graph for the number of adults expected in each genotype. Assume that each adult contributes 10 gametes to the next gene pool. Fill in the following blanks. Gametes: AA adults make gametes: Aa adults make gametes: aa adults make gametes: g. Calculate the allele frequencies in this new gene pool. Show your work.
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The initial allele frequencies are A = 0.7 and a = 0.3. b. To complete a Punnett square analysis, we need to determine the possible genotypes of the 100 zygotes produced from this gene pool. Since the initial allele frequencies are A = 0.7 and a = 0.3, we can use Show more…
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RANDOM GENETIC DRIFT Suppose that the assumptions of Hardy-Weinberg Equilibrium hold true and that the frequencies of the three possible genotypes are 0.81 (A1A1), 0.18 (A1A2), and 0.01 (A2A2). Individuals with the genotype A1A1 are the progeny of parents that each contributed an A1 allele. Because we are using p to represent the frequency of the A1 allele, if the gametes of parents join randomly, the frequency of A1A1 individuals in the progeny can be represented by p2. Similarly, q2 represents the expected frequency of individuals with the A2A2 genotype, and 2pq is the expected frequency of heterozygotes (A1A2). Therefore, we can conclude that in this population p = 0.9 and q = 0.1. This description seems reasonable enough. Up to this point all we have done is associate some mathematical notation with the genotypes that exist in a population. We can use this notation and the relationship that we have established between gametes and progeny, which is just based on Mendelian genetics, to make predictions about allele and genotype frequencies in the future. 1. Suppose that members of the above population make gametes, and release them into the water, as many marine invertebrates do (referred to as broadcast spawning). (a) What would the frequency of genotypes be in the next generation? (b) What would the frequency of genotypes be in subsequent generations? 2. Now, what if the population under consideration consisted only of a relatively small number of individuals, say 50? Considering a finite population introduces a wrinkle. What happens in finite populations that differs from the results we observed above with the model of populations of infinite size? Alternatively, what happens to genotype and allele frequencies if gametes carrying a particular allele (e.g., A1) are less viable than other gametes (i.e., selection acts against individuals carrying A1)?
Katlin K.
RANDOM GENETIC DRIFT Suppose that the assumptions of Hardy-Weinberg Equilibrium hold true and that the frequencies of the three possible genotypes are 0.81 (A1A1), 0.18 (A1A2), and 0.01 (A2A2). Individuals with the genotype A1A1 are the progeny of parents that each contributed an A1 allele. Because we are using p to represent the frequency of the A1 allele, if the gametes of parents join randomly, the frequency of A1A1 individuals in the progeny can be represented by p^2. Similarly, q^2 represents the expected frequency of individuals with the A2A2 genotype, and 2pq is the expected frequency of heterozygotes (A1A2). Therefore, we can conclude that in this population p = 0.9 and q = 0.1. This description seems reasonable enough. Up to this point all we have done is associate some mathematical notation with the genotypes that exist in a population. We can use this notation and the relationship that we have established between gametes and progeny, which is just based on Mendelian genetics, to make predictions about allele and genotype frequencies in the future. 1. Suppose that members of the above population make gametes, and release them into the water, as many marine invertebrates do (referred to as broadcast spawning). (a) What would the frequency of genotypes be in the next generation? (b) What would the frequency of genotypes be in subsequent generations? 2. Now, what if the population under consideration consisted only of a relatively small number of individuals, say 50? Considering a finite population introduces a wrinkle. What happens in finite populations that differs from the results we observed above with the model of populations of infinite size? Alternatively, what happens to genotype and allele frequencies if gametes carrying a particular allele (e.g., A1) are less viable than other gametes (i.e., selection acts against individuals carrying A1)?
Josee P.
In a population of mice, the allele frequencies at the Mc1r locus are: p = 0.6, q = 0.4. Assume the population starts out at HWE. 1. What is the starting frequency of genotype DD? Enter your answer with 2 decimal places. 2. What is the starting frequency of genotype Dd? Enter your answer with 2 decimal places. 3. What is the starting frequency of genotype dd? Enter your answer with 2 decimal places. This population begins to experience selection due to differential predation. All of the DD mice survive to reproduce, but only 75% of the Dd mice, and only 50% of the dd mice. (In this example, D allele confers darker fur, but is incompletely dominant over the d allele. Therefore, we can say there is a selective advantage provided by each copy of the D allele an individual carry.) 4. What are the genotype frequencies among mice making it to adulthood? Calculate all three, and just enter the frequency of heterozygotes in the answer box for this question. Remember to normalize so your frequencies are all out of 1. 5. Using the post-selection genotype frequencies, calculate p and q. Enter p to 3 decimal places in the answer box for this question. 6. Assuming random mating, what are the expected genotype frequencies of the offspring generation? Calculate all three and enter just enter the frequency of heterozygotes in the box, rounded to 3 decimal places. 7. Now, let's look at the same parental population in a different environment. This locality has a patchy substrate, with areas of very light and very dark rock. The relative fitness of heterozygous mice in this locality is 0.5, compared to 1.0 for both DD and dd. Calculate the post-selection genotype frequencies, the new p and q, and use the Hardy-Weinberg equations to predict the genotypes of the offspring generation. Enter the offspring heterozygote frequency in the answer box, rounded to 3 decimal places.
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