In a population of Gouldian Finches 1200 have a white breast

In a population of Gouldian Finches, 1200 have a white breast coloration and 800 have purple breast coloration. The population is at Hardy-Weinberg equilibrium and breast color is determined by a single mutation at one locus. What is the frequency of the dominant genotype if purple is the dominant trait?

Solution

1200 have white. Let the symbol for recessive trait be \"p\" and that for dominant trait be \"P\".

So, genotype of 1200 finches will be \"pp\".

Total finches=1200+800=2000

According to HW equilibrium, q^2=pp=1200/2000=0.6

q= 0.6

p=(1-q)=(1-.77)=0.23=frequency of dominant phenotype