The curly hair gene dominates the straight hair gene. Heterozygotes have wavy hair.

The curly hair gene dominates the straight hair gene. Heterozygotes have wavy hair. Determine the likelihood of having a curly baby if both parents have wavy hair.

If the gene for curly hair dominates over the gene for straight hair, and heterozygotes have wavy hair, then the problem is about incomplete dominance.

Let A – curly hair, and – straight hair; then Aa is wavy hair.

RR f Aa (in) x m Aa (in)

m / f A a A AA (j) Aa (c) a Aa (c) aa (p)
By phenotype:

25% – curly hair;

50% – wavy hair;

25% straight hair.

Phenotype cleavage – 1: 2: 1.

Answer: Parents with wavy hair have a 25% chance of having a curly baby.