Question

A boy inherited color blindness from which parent, if his father is color blind where the mother is not color blind?

• A. His father
• B. His mother
• C. Either his father or his mother
• D. Both parents; this is an example of incomplete dominance
• E. It cannot be determined

Answer 1

The correct option is B His mother

Colorblindness is a X linked recessive disorder that follows criss cross inheritance i.e., affected father pass the disease to daughter while affected mother passes it to sons. To have a colorblind son, mother should be either colorblind or carrier as son gets its X-chromosome from mother only. Affected father will not contribute disease to son as it passes Y chromosome to the son. Hence, the mother is carrier and has passed the disease to 50% of his sons.

Therefore, the correct answer is option B.