DAT Bootcamp Biology question

[nayryecal]

Hi the question says:

A student observes a population of 100 eagles in Hardy-Weinberg equilibrium. The eagle’s allele for a pointed beak is dominant, and the allele for a rounded beak is homozygous recessive. If 9 eagles were found to have a rounded beak in the population, what is the allele frequency of the pointed beak?

The answer is .70


I understand how you get .70, I just dont understand why you don't consider the heterozygous for the pointed beak and include 2pq so p^2+2pq=.91 ?

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[shulace]

The key word is allele frequency. p^2+2pq would be the dominant phenotype frequency. Saavy? =)

 

[yko0584]

Hi the question says:

A student observes a population of 100 eagles in Hardy-Weinberg equilibrium. The eagle’s allele for a pointed beak is dominant, and the allele for a rounded beak is homozygous recessive. If 9 eagles were found to have a rounded beak in the population, what is the allele frequency of the pointed beak?

The answer is .70


I understand how you get .70, I just dont understand why you don't consider the heterozygous for the pointed beak and include 2pq so p^2+2pq=.91 ?

Ok so this is how you do it. 9 round beaks is the same as 0.09, so if the recessive frequency
q^2 = 0.09
q = 0.3

p + 0.3 = 1
p = 0.7

You don't consider the heterozygote frequency because they have to specifically ask for it, but in total homozygous and heterozygous dominant should equal 0.70.