Question

"Colorblindness is a recessive, X-linked trait. In marriages between a man who is colorblind and a woman who is a carrier, what percentage of the children can be expected to be daughters who are colorblind?"

a. 25%
b. 0%
c. 100%
d. 50%

Answer 1

In a marriage between a colorblind man and a carrier woman, there is a 50% (option D) chance that their daughters will be colorblind, as they can inherit the affected X chromosome from both parents.

Step-by-step explanation:

Colorblindness is a recessive, X-linked trait. When a colorblind man (Xy) marries a carrier woman (XCXc), their children have different probabilities of inheriting this trait. Since the man can only pass on his Y chromosome to sons and his X chromosome to daughters, all of their sons will have normal color vision (receiving the normal X from their carrier mother). Their daughters, however, will receive one X chromosome from each parent.

Considering the genetics behind this, the possibility of a daughter being colorblind is represented as the cross XCXc (mother) × XcY (father). We can map this out in a Punnett square:

• XC from mother and Xc from father results in a carrier daughter (XCXc).
• Xc from mother and Xc from father results in a colorblind daughter (XcXc).

Each daughter has a 50% chance of being a carrier (just like the mother) and a 50% chance of being colorblind. Hence, the answer to the question of what percentage of daughters can be expected to be colorblind is d. 50%.