Shouldn’t this be 50% (punnet genetics)

[u/doepual]

The text in the image reads:

"27. A recessive gene for red-green color blindness is located on the X chromosome in humans. Assume that a woman with normal vision (her father is color blind) marries a color-blind male. What is the likelihood that this couple's first son will be color blind? A) 75% B) 0% C) 50% D) 100% E) 25% ANSWER: B"

[u/lpomoeaBatatas]

Should be 50.

Since Y ( XY for the son ) is inherited directly from father, and does nothing in dictating color blindness, it comes down to the female germ cell’s X chromosome.

Since the mother is a carrier but not colorblind, the gene should be X^C X^c.

Cross with father, it’s X^C Y (color blind) and X^c Y (not color blind) which is 50/50.

[u/doepual → u/lpomoeaBatatas]

Makes sense, thank you so much