Colorblindness is Xlinked and recessive a If a colorblind ma

Color-blindness is X-linked and recessive. a. If a color-blind male marries a homozygous normal woman, what chance is there for the children to be color-blind? Why is it so commonly believed that women cannot be color-blind? A color-blind man has a color-blind sister and his mother has normal vision. What is the genotype, as to color vision, of this man\'s mother and his father?

Solution

a. Chances for the children to be colour-blind is zero. Because gene responsible for the colour-blind is presenet on X chromosome. So if the child will be boy then he will have XY ( X from mother and Y from father) and in this case father is colour blind but he is passing Y chromosome to his child. If the child will be girl then she will have XX (one X from father and one X from mother) and in this case father will pass X chromosome with colour blind gene and mother will pass normal X chromosome. Still girl child will not be colour blind because for a girl to be colour blind both X should have colour blind gene. If only one X will have colour blind gene then that girl will become carrier. Hence the chances for the chindren to be colour-blind is zero in this case.

b. A women will be colour-blind only in the case, when her father is colour-blind and her mother is either colour-blind or carrier. This situation is very rare. Thats why it is commonaly believed that women cannot be colour-blind. In the case of male if only X will have colour blind gene, he will be colour blind, but a female to be colour blind should have both X with clolour- blind gene.