4. In purebred Holstein cattle, about one calf in 100 is spotted red rather than black....

Frequency of Red spotted Calf = 1/100 = 0.01

Since this is a recessive trait, only Homozygous recessive individuals display this trait. Therefore;
Frequency of Homozygous recessive phenotype = q² = 0.01

a)

Frequency of recessive (red) allele = q = 0.1

b)

Frequency of the dominant (back) allele = p = 1 - q = 1 - 0.1 = 0.9
Frequency of the Black Homozygous cattle = p² = 0.9 * 0.9 = 0.81

c)

Frequency of the Black Heterozygous cattle = 2pq = 2 * 0.9 * 0.1 = 0.18