Final answer:
The probability of a child having a widow's peak from a mother with genotype ww and a father with genotype Ww is 50%.
Step-by-step explanation:
The question pertains to genetic inheritance and the calculation of probabilities for dominant and recessive traits, specifically examining the likelihood that offspring will have a widow's peak. A widow's peak (W) is a dominant trait, while a straight hairline (ww) is recessive. With a mother who has the genotype ww (homozygous recessive for a straight hairline) and a father who has the genotype Ww (heterozygous with a widow's peak), we can use a Punnett square to determine the possible genotypes of their children.
To calculate the probability of their child having a widow's peak, you create a Punnett square with the mother's alleles (w w) on one side and the father's alleles (W w) on the other. This yields the following genotypes for the potential offspring: Ww, ww, Ww, ww. Since Ww represents a widow's peak, and we have seen it twice in the four possible outcomes, the probability of a child having a widow's peak is 2/4 or 50%.