Recall that pigmented eyes (P) are dominant to nonpigmented (p), and dimpled chi

Question

Recall that pigmented eyes (P) are dominant to nonpigmented (p), and dimpled chins (D) are dominant to nondimpled chins (d)

A pigment-eyed, dimple chinned man marries a blue-eyed woman without a dimpled chin. Their first born child is blue-eyed and has a dimpled chin.

a) What are the possible genotypes of the father?

b) What genotype is the mother?

c) What alleles may have been carried by the father’s sperm?

Suppose a dimple-chinned, blue-eyed man whose father lacked a dimple marries a woman who is homozygous recessive for both traits.

a) What is the expected genotypic ratio of children produced in this marriage?

b) What is the expected phenotypic ratio?           

Explanation / Answer

1). A pigment-eyed, dimple chinned man (PpDD) marries a blue-eyed woman without a dimpled chin (ppdd), they will have the offspring with the following genotypes.

a). The possible genotypes of the father are either PpDd or PpDD. The father is heterozygous for the eye colour because the child has blue eyes, but the dimpled chin alleles may be either homozygous dominant or heterozygous.

b). The genotype of mother is ppdd, she must be homozygous recessive for both the alleles.

c). Alleles carried by the father's sperm are, p and D. As the child is blue-eyed, he has to inherit one recessive allele each of their parents.

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