4. in humans, red - green colorblindness is a sex - linked recessive trait. if a man and a woman produce a…

4. in humans, red - green colorblindness is a sex - linked recessive trait. if a man and a woman produce a color - blind son, which of the following must be true?\na. the father is colorblind.\nb. both parents carry the allele for colorblindness.\nc. the father carries the allele for colorblindness.\nd. the mother carries the allele for colorblindness.

4. in humans, red - green colorblindness is a sex - linked recessive trait. if a man and a woman produce a color - blind son, which of the following must be true?\na. the father is colorblind.\nb. both parents carry the allele for colorblindness.\nc. the father carries the allele for colorblindness.\nd. the mother carries the allele for colorblindness.

Answer

Brief Explanations:

Since red - green colorblindness is a sex - linked recessive trait (on the X chromosome). A son has one X chromosome (from the mother) and one Y chromosome (from the father). For the son to be colorblind ((X^{c}Y)), he must have received the (X^{c}) (colorblind allele) from his mother. The father gives the Y chromosome. The father does not need to carry the colorblind allele (he could be (X^{C}Y)) and the mother must be a carrier ((X^{C}X^{c})) or colorblind ((X^{c}X^{c})).

Answer:

d. The mother carries the allele for colorblindness.