Please help The allele for polydactyly 6 fingers or toes is

Please help

The allele for polydactyly (6 fingers or toes) is dominant to the more common allele for 5 fingers. If 90 percent of the population has 5 fingers and 8 percent of the population is heterozygous, what is the frequency of the polydactyl allele?

a) 0.004

b) 0.65

c) 0.02

d) 0.06

e) 0.90

Solution

Polydactyly is a congenital deformity in which a person has more than 5 fingers per hand or 5 toes per foot.

Polydactyly is an autosomal dominant trait, but the allele frequency is now so low that it is a rare condition.

Usually it is believed that if a trait is dominant, it will have a high frequency. In other words, if the trait is dominant, it should be more common in the population. This is not necessarily true, and a good example of this is polydactyly, having extra fingers.

The Hardy-Weinberg principle states: The frequency of an allele in a population will remain constant from generation to generation.

Remember the basic formulas:

p^2 + 2pq + q^2 = 1 and p + q = 1

p = frequency of the dominant allele in the population

q = frequency of the recessive allele in the population

p^2 = percentage of homozygous dominant individuals

q^2 = percentage of homozygous recessive individuals

2pq = percentage of heterozygous individuals

In the given question 90 percent of the population has 5 fingers and 8 percent of the population is heterozygous;

The frequency of the \"a\" allele. Answer: The frequency of aa is 90%, which means that q^2 = 0.90, by definition. If q^2 = 0.90, then q = 0.94, again by definition. Since q equals the frequency of the a allele, then the frequency is 94%.

The frequency of the \"A\" allele. Answer: Since q = 0.94, and p + q = 1, then p = 0.06; the frequency of A is by definition equal to p, so the answer is 6%. Therefore the frequency of polydactyly allele p is 0.06. Therefore option d is correct.

The frequencies of the genotypes \"AA\" and \"Aa.\" Answer: The frequency of AA is equal to p^2, and the frequency of Aa is equal to 2pq. So, using the information above, the frequency of AA is 0.36% (i.e. p^2 is 0.06 x 0.06 = 0.0036) and Aa is 5.64% (2pq = 2 x 0.06 x 0.94 = 0.0564).