Question

A colorblind man ${ X }^{ c }{ Y }$ has a color-blind sister ${ X }^{ c }{ X }^{ c }$ and a normal brother (XY). What is the genotype of father and mother?
A. ${ { X } }^{ C }{ Y }$, ${ { X } }^{ C }{ X }^{ C }$
B. ${ { X } }^{ C }{ Y }$, ${ { X } }^{ C }{ X }$
C. XY, ${ { X } }^{ C }{ X }^{ C }$
D. XY, ${ { X } }^{ C }{ X }$

Answer 1

Hint: A genetic condition where a person is unable to see certain colors. It is carried from mostly mothers to their sons and rarely in daughters because it is an X-linked disease.

Complete answer:
Color blindness is an X-linked disease or mutation. It has three conditions: Red-Green color blindness, Blue-Yellow color blindness, and Total color blindness. If one brother is normal then it means one of the X chromosomes does not carry any color-blind trait. So the mother has two X chromosomes out of which one of the X chromosomes do not contain color blind traits. Hence, the mother is the carrier of the color blindness.

Additional Information: Colour blindness is a color deficiency or color vision deficiency where a person cannot see colors or maybe the differences in colors normally. It usually happens between the green and the red colors as the person cannot differentiate between them. This may occur due to the developmental problem in some of the sets of the cones which are color sensing in the eye. This disease has been observed more in the case of males than females because of its gene which is present on the X chromosome. The females have two X chromosomes if one chromosome has defected than it can be compensated by the other resulting in the normal or carrier female while in the case of males only one X chromosome is present which is if defected will result in the genetic disorder if the chromosomes ace recessive gene of the disease.

So, the correct answer is ‘${ { X } }^{ C }{ Y }$, ${ { X } }^{ C }{ X }$’.
Note: The Extraordinary facts related to the vision of colors were the first scientific paper which was published in 1786 by John Dalton. It was also called Daltonism after the name of the scientist. This disease does not have any cure, it can be detected by the Ishihara color test which is most commonly used.