Question

Given the following information, how would you determine the allele frequencies for the B allele and the b allele? How would you determine the genotype frequencies for the BB, Bb, and bb genotypes?

In a population of 200 students, 98 are homozygous dominant for brown hair (BB), 84 are heterozygous (Bb), and 18 are homozygous recessive (bb).

Answer 1

Please read this to understand.

Explanation:

When the number of individuals are already mentioned derive the frequency in 100 individuals: for this question which will be as following --

Number of homozygous dominant 49% ( `B^2`)
Number of heterozygous dominant 42% ( `2Bb`)
Number of homozygous recessive 9% (`b^2`)

(There are two alleles B and b)

Now you can derive the frequency of alleles:

Frequency of allele B = `sqrt(.49)` = .7
Frequency of allele b = `sqrt(.9)` = .3

(According to Hardy Weinberg principle --
sum of all the frequencies of alleles = 1
in this case .7 + .3 = 1 )