Red-green color blindness is an X-linked recessive disorder. A woman with normal vision whose father was colorblind has children with a man with normal color vision. What is the probability that their first child will be colorblind?
A) 1/4
B) 1/2
C) 3/4
D) 0
E) 1

The woman is a carrier. she must have obtained the X-linked recessive allele from the father XCY.(assuming C stands for color blindness)Therefore she carries the X-linked gene for color blindness on one of her X -chromosomes as a carrier. (XCX), or (XXC)

if she is now crossed with the husband with normal vision;

then ; XY vs XX

the sex and inheritance of the colorblindness is as follows

XCX- carrier girl

XX- normal girl

XCY or XY. or vice-versa (depending on which of the X chromosomes carries the C allele)

The probability depends on the sex of the child. The first child can be a boy or a girl. Assuming the first child is a boy then it can be either of the two boys so 1/2. The girls can not be colorblind because the father who should give the colorblindness X -chromosomes for XX sex-chromosomes is normal . Therefore their probability is not relevant here.

Red-green color blindness is an X-linked recessive disorder. A woman with normal vision whose father was colorblind has children with a man with normal color vision. What is the probability that their first child will be colorblind? A) 1/4 B) 1/2 C) 3/4 D) 0 E) 1

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Red-green color blindness is an X-linked recessive disorder. A woman with normal vision whose father was colorblind has children with a man with normal color vision. What is the probability that their first child will be colorblind?
A) 1/4
B) 1/2
C) 3/4
D) 0
E) 1