Question

You are a genetic counselor. As a genetic counselor, you know:

-Dry (as opposed to wet) earwax is an autosomal recessive trait.

-Red-green colorblindness is an X-linked recessive trait.

-Sickle-cell anemia is an autosomal recessive trait.

-The genes for these traits (see above) are located on different chromosomes.

You are counseling a woman and a man, as described below.

Question A. The woman is heterozygous for wet earwax. She has red-green colorblindness. What is the woman’s genotype?

Question B. What are the possible gamete genotypes that she can produce?

Question C. The man has dry earwax. He not have red-green colorblindness. What is the man’s genotype?

Question D. What are the possible gamete genotypes that he can produce?

Question E. The woman and the man are planning to have children. What is the probability that a daughter will have neither dry earwax nor red-green colorblindness? What is the probability that a son will have neither dry earwax nor red-green colorblindness? Hint: Complete a Punnett square

Answer 1

A. WwX^*X^*

B. WX^* and wX^*

C. wwXY

D. wX and wY

E. Probability of daughter with neither dry earwax nor red-green Colorblindness = 1/2. (there will not be any daughter with this red-green Colorblindness, however one daughter will have wet earwax and one will have dry earwax.)

Probability of son with brighter dry earwax nor red-green Colorblindness = 0/2 = 0. (both sons will have red-green Colorblindness. See punnet square in attached figure).