Question

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?

Answer 1

Answer:

The probability of their first child being colourblind is 1/4

Explanation:

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.

In an X-linked condition, the males only need to get one copy of the affected allele to have the condition and this copy is also inherited by a female offspring.

So in this case, the woman receives the affected recessive allele copy from her dad but since she still has normal vision, she received the normal copy from her mom so she is heterozygote for the trait.

The woman with normal color (XRXr) has a father who is color blind (XrY) has children with a normal man (XRY)

The cross would be

XRXr x XRY

XR Xr

XR XRXR XRXr

Y XRY XrY

Probably of having an affected child is 1/4. Thus, the probability of their first child being colourblind is 1/4