Copy of Answer Sheet - Lab #8- Natural Selection

ANSWER SHEET FOR GENETICS LAB #8 – Natural Selection NAME: Lab Section: _______________ Calculate how many generations it would take to reduce the frequency of the recessive allele from q 0 to q n : q 0 q n Change in q n 0.5 0.1 -0.4 0.1 0.01 -0.09 0.01 0.001 -0.009 Activity 1 Estimate p and for the given model after 5, 10, 50, and 100 generations 𝑤 Generation w =1, 1, 0.99 w = 1, 1, 0.9 w = 1, 1, 0.5 w = 1, 1, 0 5 0.5 10 50 100 Generation w =1, 0.995, 0.99 w = 1, 0.95, 0.9 w = 1, 0.75, 0.5 w = 1, 0.5, 0 5 10 50 100 Generation w =0.99, 0.995, 1 w = .9, 0.95, 1 w = .5, 0.75, 1 w = 0, 0.5, 1 5 10 50 100 Peppered moth . Suppose a population of moths with an initial p value of 0.8 invade a light colored habitat. Use Populus to predict what would p and be after X generations. 𝑤 # generations 5 10 15 20 25 30 p = q = Peppered moth. Suppose these same moths with an initial p = 0.8 invade an area with a dark background, what would p and be after X generations. 𝑤 # generations 5 10 15 20 25 30 p = q =

Activity 2 Selection for the Heterozygote Generation w = 0.99, 1, 0.99 w = 0.3, 1, 0.5 w = .0.1, 1, 0.9 w = 0.9, 1, 0.1 5 10 50 100 Sickle cell anemia Expected equilibrium frequency for q ? ___________ for p ? ______________ Number of generations to reach this equilibrium with an initial p value of 0.2 _______________, with an initial p value of 0.9 __________? Use Populus ( vs p graph) to estimate at this equilibrium ____________. 𝑤 𝑤 ANSWER SHEET QUESTIONS 1. Was the efficiency of selection different for selection against the recessive genotype versus selection against the recessive allele? If so, why was this? 2. If there was complete (100%) selection against an uncommon deleterious recessive genotype ( aa ) in the human population, would you expect to observe much of an effect on the frequency of the a allele in your lifetime? Why or why not? 3. Why did it take more generations of complete selection to reduce q from 0.1 to 0.01 (a 0.09 change) compared that for a 0.5 to 0.1 reduction (a larger, 0.4 change)? Explain. 4. Although selection operates against deleterious alleles in populations, they are rarely lost from these populations. For example, most deleterious recessive alleles in population have equilibrium q values slightly above 0. Why might that be?