Question

Red-green color blindness is a recessively inherited disorder that affects 7% of the male population but only 0.4% of the female population. Given what you know about disease inheritance and gender determination, why do you think color blindness is so much more common in men than women?

Answer 1

Answer:

Men express all the X-linked genes present in their genome.

Explanation:

Human males have one copy of X and one copy of Y chromosomes. They express all the alleles present on their X chromosome irrespective of its dominant or recessive nature. This occurs because males do not have a second copy of the X chromosome to carry another allele for the same gene. Color blindness is caused by a recessive allele present on the X chromosome. Males carrying one copy of this allele exhibit the disease while females need two copies of the allele of color blindness to express the disease. Therefore, males are more frequently affected by this disease.