MCAT Question A Day - 9/27/14 - Answer!
Colorblindness is a sex-linked recessive trait. A woman is horn colorblind. What can be said with certainty?
A. Her father and mother are colorblind.
B. Her mother and daughter are colorblind.
C. Her father and son are colorblind.
D. Her father is colorblind, but her son mayor may not be.
C is correct. The woman has two recessive Xs. Her mother gave her one X and her father gave her one X. Her father only had one X to start with, so it must have been recessive and he must have been colorblind. Her son will receive a recessive X from her and a Y from his father so he will be colorblind.
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C is correct. The woman has two recessive Xs. Her mother gave her one X and her father gave her one X. Her father only had one X to start with, so it must have been recessive and he must have been colorblind. Her son will receive a recessive X from her and a Y from his father so he will be colorblind.
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