Question

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 lik couple's first son will be color blind? A)0% B) 25% C) 50% D) 75% E) 100%

Answer 1

Answer:

25%

Explanation:

Based on Mendelian inheritance 4 offs-pings were produced,

XX  haemophiliac first  girl

XX carrier  girl

XY HAEMOPHILIAC first  boy

XY normal second boy

Since the father of the woman is  haemophiliac, then she is a carrier fro haemophilia  (although with normal vision) who inherited the allele of the the sex-linked X chromosomes from the father.