A population of poisonous frogs is sampled and assessed for skin color. Skin col

Question

A population of poisonous frogs is sampled and assessed for skin color. Skin color is determined by alleles at one locus; allele “C” is for Blue skin and allele “c” is for red skin. “C” is completely dominant to “c”.

         Assume that this population is in Hardy-Weinberg Equilibrium and that the population’s features and the locus for skin color satisfy the assumptions for the H-W Law. From a population of 462 poisonous frogs, 174 frogs have blue skin and 288 frogs have red skin.

a. What is the frequency of the allele for red skin, allele “c”?

b. What is the frequency of allele C?

c. What is the expected frequency of the “cc” genotype in the next generation of that population

d. What is the expected frequency of the “Cc” genotype in the next generation of that population?

Explanation / Answer

From Hardy-Weinberg equation-

                                                            p2 + 2pq + q2 = 1 ....(1) & p + q = 1 .....(2)

Where, p = frequency of the dominant allele (C in our case)

q = frequency of the recessive allele (c in our case)

p2 = percentage of homozygous dominant individuals (blue skin)

q2 = percentage of homozygous recessive individuals (red skin)

2pq = percentage of heterozygous individuals (blue skin)

a) Now according to the question, out of 462 frogs, 288 frogs have red skin.

Therefore red skin frog percentage (q2) = (288/462) = 0.6234 (up to 4 digits)

Therefore, frequency of recessive allele 'c' for red skin (q) = ?q2 = 0.7895 (up to 4 digits)

So, frequency of the allele for red skin, allele “c” is 0.7895.

b) From equation (2) we can find the value of p.

Therefore, p = 1- 0.7895 = 0.2105

So, frequency of allele C is 0.2105.

c) Now, probability of c allele is mating with c allele = 0.7895 x 0.7895 = 0.6233 (up to 4 digits)

So, expected frequency of the “cc” genotype in the next generation of that population is 0.6233.

d) Now, probability of C allele is mating with c allele = 0.2105 x 0.7895 = 0.1662 (up to 4 digits)

So, expected frequency of the “Cc” genotype in the next generation of that population is 0.1662.

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