Polydactyly is a trait found in cats and humans in which a person (or cat) has 6 digits per hand or paw. The allele for polydactyly is rare but dominant. If a man who is heterozygous
for this trait marries a woman with 5 fingers, what are the chances that they will have a child
with polydactyly?

1/2 or 50%

Explanation:

This question involves a single gene coding for the number of digits per paw in cats or humans. The allele for polydactyly i.e six digits (P) is dominant over the allele for normal number of digits i.e 5 (p).

According to this question, If a man who is heterozygous (Pp) for this trait marries a woman with 5 fingers (pp), the following gametes will be produced by each parent:

Pp : P and p

pp : p and p

Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced:

Pp, Pp, pp and pp

The offsprings with genotype Pp will have polydactyl, hence, the chances that they will have a child with polydactyly is 1/2 or 50%.

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