Genetics Problem Set - Sex Linkage

Sex-linked Traits! Don't forget to use your X's and Y's.

Female _____ Male _____ Traits only travel on _____

1. In humans, colorblindness is a sex-linked recessive trait. The dominant allele results in normal vision. What would be the results of the following crosses?

A) A man who is not colorblind and a woman who is colorblind.

B) A woman who is not colorblind and is heterozygous and a man who is not colorblind.

2. Baldness is a sex-linked trait found on a recessive allele. A head of full hair is the dominant trait. What would be the results for the following crosses?

A) A female who is homozygous for normal hair a man who is bald.

B) A female who is bald with a man who has a full head of hair.

3. In humans, a sex-linked dominant allele, R, produces rickets, a skeletal disorder. The recessive allele, r, results in normal skeletal development. What would be the results of the following crosses?

A) A man with rickets and a woman who does not have rickets.

B) A woman who has rickets (but whose father did not) and a man who does not have rickets.

Extra Credit

4. In chickens, the Bar feather pattern is due to a sex-linked dominant allele, B. The recessive allele, b, results in non-Bar feathers. Another little situation occurs in chickens. The female is XY and the male is XX. The traits still travel on the X. Remember, the Y is missing stuff. Do the following crosses using all five traits.

A) A Bar hen is mated with a non-Bar rooster.

B) A non-Bar hen is mated to a Bar rooster whose mother was non-Bar.