Question

For a gene that determines wing color in butterflies, there are three possible genotypes: BB (blue wings), bb (white wings), and Bb (white wings with blue blotches). A sample of 100 butterflies was collected, and the following was observed:

Wing Color Number of Butterflies
blue 60
white with blue blotches 30
white 10


What is the frequency of the Bb genotype in this population if it is in Hardy-Weinberg Equilibrium?

Answer 1

Answer: The frequency of the b allele is calculated as follows: since there are 2 alleles in each organism, total number of genes is 200. The number of white alleles is 10*2+30 (since there are 2 copies of the alleles in white organisms and 1 copy of the b allele in the white wings with blue blotches). So the total number of white alleles is 20+30=50 white alleles. The frequency of the white allele is then 0.25. So the frequency of the blue allele is 1-0.25=0.75. Since heterozygous term is 2*p*q, the frequency of the Bb genotype is 2*0.25*0.75=0.375. Hope that helped!