Question

a colorblind man marries a female who is carrier for colorblindness. What is the probability that they will have a child who is colorblind​

Answer 1

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These genes come from the carrier mother of the F1 generation. So we can see that the probability of the grandsons who are color-blind will be 28 or 14 which is 0.25. So, the correct answer is, '0.25.

Answer 2

only 25% of their children will be colorblind. Which also means 50% of grandsons will be colorblind.
Therefore the following calculations can be made:
If the total number of grandsons from four crosses of F1 progeny where each member of F1 mates with a normal person is 8, then out of these 8 only two grandsons will be color blind. These genes come from the carrier mother of the F1 generation. So we can see that the probability of the grandsons who are color-blind will be 2/8
or 1/4
which is 0.25.