A recently arisen volcanic island is colonized by a snail species deposited on t
ID: 91584 • Letter: A
Question
A recently arisen volcanic island is colonized by a snail species deposited on the island by strong hurricane winds. These snails exhibit variation in shell color. Shell color is controlled by a single gene, such that individuals with the genotype AA are dark, individuals with the genotype Aa are light brown, and individuals with the genotype aa are white (i.e., assume that the alleles are co-dominant). Assume that 30% of the original colonists are dark, 20% are brown, and 50% are white.
a. What will the relative Allele frequencies be at Hardy-Weinberg equilibrium?
b. What will the relative genotype frequencies be at Hardy-Weinberg equilibrium in the above example in the next generation?
c. Are the genotype frequencies you calculated in question (b) different from the original genotype frequencies given in the question? Is so, why (given only the information provided in the question)? If not, why might this be (given only the information provided in the question)?
d. Assuming nothing changes from the situation in question (b), make predictions about what will happen with the population’s genotype frequencies in the next several generations? Justify your predictions in detail.
Explanation / Answer
a) The relative allele frequencies at Hardy-Weinberg's equilibrium are 0.3 for dark, 0.2 for brown and 0.5 for white colored snails.
b) The relative genotype frequencies at Hardy-Weinberg's equilibrium are as follows,
The frequency of AA snails = p2 = (0.3)2 = 0.09
The frequency of Aa snails = 2pq = 2 (0.2) = 0.4
The frequency of aa snails = q2 = (0.5)2 = 0.25
c) The genotype frequencies calculated is different from the original genotype frequencies given in the question because the population is not at Hardy-Weinberg's equilibrium since p2 + 2pq + q2 is not adding upto 1.
d) The population's genotype frequencies in the next several generations will continuously change due to the effects of nonrandom mating, genetic drift and mutation.