Question

A rare form of heredity color-blindness occurs on the small island of Pingelap in the south Pacific. People with most forms of color-blindness actually are able to see some colors, but those with the Pingelap disease see no colors at all. The Pingelap eye disease is a genetic condition, more precisely, an autosomal recessive disorder. Assume that 4% of the Pingelap population has the disease. Also assume, for now, that the Pingelap population is in Hardy-Weinberg equilibrium for the eye disease gene.

For each of the questions below, show how you arrive at your answer.

1) What is the frequency of the allele for the eye disease in the Pingelap population?

2) What is the frequency of the normal vision allele?

3) What proportion of the population are carriers of (heterozygotes for) the eye disease allele?

4) What proportion of the population does not carry any copy of the eye diseases allele?

5) Consider only the allele that causes eye disease. What percentages of this allele are found in heterozygotes and what percentage in homozygotes?

6) In reality, how might this situation violate the conditions for Hardy-Weinberg equilbrium?

Answer 1

Answer:

1).

Frequency of the disease = q^2 = 4% = 0.04

2).

Frequency of diseased allele = q = SQRT of 0.04 = 0.2

Frequency of normal vision allele = p = 1-q = 1 – 0.2 = 0.8

3).

Frequency of carriers = 2pq = 2 * 0.8 * 0.2 = 0.32 = 32%

4).

Proportion of the population does not carry any copy of the eye diseases allele = 100% - (4% + 32%) = 64%

5).

Heterozygotes = 32%

Homozygotes = 4%

6).

The following situations violate the conditions for Hardy-Weinberg equilibrium:

a). Mutation,

b). Non-random mating

c). Gene flow

D). Genetic drift

E). Natural selection.