Answer:
25%
Explanation:
Let's assume that the recessive allele "p" imparts diseased conditions in the homozygous genotypes. The genotype of each of the carrier parents would be "Pp". A cross between Pp and Pp would produce progeny in the following phenotype ratio=
Pp x Pp= 3/4 Normal : 1/4 Affected.
Therefore, there are 1/4 or 25% chances for this couple to have a child with PKU.
