Within a population of butterflies , the color brown (B) is dominant over the color white(b) .40% of all butterflies are white. Given this simple information , calculate the percentage of butterflies in the population that are heterozygous ?

How to calculate the frequency of homozygous dominant?

1 Answer
Dec 19, 2015

#12%#

Explanation:

Alleles: #p+q=1#

#p="frequency of the dominant allele"#
#q="frequency of the recessive allele"#

Genotypes: #p^2+2pq+p^2=1#

#p^2="frequency of homozygous dominant genotype"#
#2pq="frequency of heterozygous genotype"#
#q^2="frequency of homozygous recessive genotype"#

We know that the frequency of homozygous recessive is #0.40%#, which, as a decimal, is equal to #0.004#.

This means that

#q^2=0.004#

Take the square root of both sides to find #q#.

#q=sqrt(0.004)=0.0632#

To find #p#, use the first equation.

#p+0.0632=1#

#p=0.9368#

To find the frequency of the heterozygous population, find #2pq#.

#2pq=2(0.0632)(0.9368)=0.1184#

Rounded to two significant digits, this is #0.12# or #12%# of the population.