In Humans, Red-Green Color Blindness Is Caused by a Recessive

Short Answer

In humans, red-green color blindness is caused by a recessive allele on the X chromosome. Therefore, if a female who is a carrier for the allele that causes color blindness marries a male who is color blind, the probability that their first child will be a girl who is color blind is 25%. This assumes normal dosage compensation where the X that is inactivated in females varies randomly from cell to cell. But suppose the normal mechanism of dosage compensation is altered so that the X that is inactivated in any given female is random but the same X is inactivated in every cell of her body. In this case, what is the probability that their first child would be a girl with color blindness? ( Express the probability as a percent. Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )