Widow's peak (W) is a dominant gene for hairline while a straight hairline is recessive (w). Determine the Phenotype frequency, Genotype frequency and Allele Frequency if a heterozygous dominant crosses with a homozygous recessive

Phenotype frequency ( widow's peak ) = 0.5

Phenotype frequency ( straight hairline ) = 0.5

Genotype frequency ( Ww ) = 0.5

Genotype frequency (ww) = 0.5

Allele frequency ( W ) = 0.25

Allele frequency ( w ) = 0.75

Explanation:

Given, Widow's peak (W) is dominant over straight hairline (w).

Parent 1: heterozygous dominant = Ww

Parent 2: homozygous recessive = ww

When Ww X ww :

     W      w

w  Ww   ww

w  Ww   ww

Half of the offspring are Ww and other half are ww so genotype frequency of Ww is 0.5 and of ww is 0.5. Phenotype ratio for widow's peak (Ww) is 0.5 and for straight hairline (ww) is 0.5.

Allele frequency = Number of that allele / Total number of alleles

f(W) = 2 / 8 = 0.25

f(w) = 6 / 8 = 0.75

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