Question

The allele for a widow's peak has complete dominance over the allele for a straight hairline (w). What is the probability of two parents heterogeneous for a widow's peak (Ww) having an offspring without a widow's peak?

Answer 1

The ratio by punnet square will be:
1 : 2 : 1
(WW : We : ww)

so the %age will be 25%

Answer 2

Answer:

Genotype for widow's peak of both male and female is same i.e. heterozygous dominant (Ww).

Gametes formed by male = W and w,

and that of female = W and w

Cross would result in the formation of WW, Ww, and ww in 1 : 2 : 1.

One out of four carries homozygous recessive trait i.e. ww or straight hairline.

Hence, the probability of offspring without widow's peak is 1/4 or 0.25.