Question

4. A woman who is heterozygous for freckles and a carrier for PKU disease marries a

Answer 1

Answer:

Freckles, no PKU- 9/16

Freckles, PKU- 3/16

No freckles, no PKU- 3/16

No freckles, PKU- 1/16

Explanation:

This question involve two distinct genes; one coding for possession or not of freckles and the other for PKU disease in humans. Allele for freckles (F) and no PKU (P) are dominant over the alleles for no freckles (f) and PKU (p) respectively.

N.B: Possession of freckles is a dominant trait i.e. FF and Ff possess freckles

If a woman who is heterozygous for freckles and a carrier for PKU disease (FfPp) marries a man who is also heterozygous for freckles and a carrier for PKU disease (FfPp), they produce the following gametes: FP, Fp, fP, and fp

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

Freckles, no PKU (F_P_) - 9/16

Freckles, PKU (F_pp) - 3/16

No freckles, no PKU (ffP_) - 3/16

No freckles, PKU (ffpp) - 1/16