Can you please explain why the answer to 16c is p=1? I keep getting p=0 when usi
ID: 205578 • Letter: C
Question
Can you please explain why the answer to 16c is p=1? I keep getting p=0 when using p=(h-1)/(2h-1).
16. In your research lab, you have four separate populations of the roundworm C. elegans. You are studying the dynamics of the A locus, which has two alleles, called Ai and A2. Assume no drift (because the lab population (a) Below is a table of relative fitness values for each genotype. Values for populations 1 and 4 are all provided. In population 2, A2 is lethal when homozygous, and heterozygotes have fitness exactly intermediate sizes are huge), no mutation, no migration, and random mating within each population. Fill in the missing values for populations 2 and 3. Base your answers on the following information between the homozygotes. In population 3, A2 homozygotes have relative fitness 0.8, and Ai is completely recessive W11 W12W22 population 0.90.8 population 2 0.50 population 3 0.80.8 1.1 0.9 population 4 1 You start an experiment, giving Al an initial frequency p = 0.01 in each of the four separate populations. (b) Will the frequency of A1 change more rapidly in population 1 or 3 over the first few generations? Why? (You may answer only with words, or you may employ an equation if you prefer.) The frequency of Ai will increase in both populations, but much more quickly in population I because only there does AiA2 have higher fitness than A2A2. The fitness advantage of AiAi doesn't matter much at first because when Ai is rare, it is mostly found in heterozygotes. Alternative answer with math: s = 0.2 in both populations, h = 0.5 in pop 1, and h = 1 in pop 3, with small initial p, the fitness increase is governed by q(1 - h), which is larger in population 1 After running your experiment for many thousands of generations, you would like to compare the allele frequencies you observe against the theoretical expectations. Answer each of the next two parts with a number (or partial credit for a qualitative description), and also explain in a few words how you came to that answer (c) What equilibrium frequency of Ai do you expect for population 3? Explain. Allele A1 provides a fitness advantage when homozygous, and no fitness cost (relative to A2A2) when heterozygous. It is therefore favored by directional selection and will eventually fix, i.e., reach an equilibrium frequency of (d) What equilibrium frequency of Ai do you expect for population 4? Explain. Fitness is highest for heterozygotes, so this is a case of overdominant selection and both alleles will be maintained at equilibrium. Also, the equilibrium frequency of Ai will be more than 0.5 because AiAi has higher fitness than A2A2 More precisely, s = 0.1 so h =-1, yielding p = (h-1)/(2h-1)-(-2)/(-3) = 0.667Explanation / Answer
When heterozygous and one of the homozygous allele frequencies are same, it is known as the selection against dominant allele. This eliminates the dominant allele (A2) from the population by reaching a equilibrium frequency of 1 (frequency of A1).
Here, p=(h-1)/(2h-1) formula should be used only when overdominance occurs.