A father who has red-green color blindness and a mother who has normal vision may have the following child:
A) Color blind male child
B) Color blind female child
C) Normal vision male child only
D) Normal vision female child only.
E) Normal vision male or female child.

Question

A father who has red-green color blindness and a mother who has normal vision may have the following child:  
A) Color blind male child
B) Color blind female child
C) Normal vision male child only
D) Normal vision female child only.
E) Normal vision male or female child.

Quizplus · Accepted Answer

Color blindness is a sex-linked disorder and is carried on the X chromosome. Since females have two X chromosomes, if the mother is a carrier of the color blindness gene (despite having normal vision), she can pass on the gene to her son without being affected by the disorder herself. However, if the father has color blindness and passes on his affected X chromosome to his son, then the son will have color blindness. As for daughters, they need both X chromosomes to carry the color blindness gene to be affected. In this case, the father can only pass on his Y chromosome to his daughters, so they will not be affected by the disorder. Therefore, there is a 50% chance of having a color blind male child and a 50% chance of having a normal vision male or female child.

A Father Who Has Red-Green Color Blindness and a Mother