Color blindness is a sex-linked trait. As such, if a child is color blind, we can be assured that the child's genotype includes:
A) a recessive gene on the X chromosome inherited from his mother
B) a dominant gene on the X chromosome inherited from his mother
C) a recessive gene on the Y chromosome inherited from his father
D) a dominant gene on the X chromosome inherited from his father

Question

Quizplus · Accepted Answer

Sex-linked traits are those that are determined by genes on the 23rd chromosome pair. If a normally recessive allele appears on the male's X chromosome, there often is no allele on the Y chromosome to offset it, and the recessive trait will be expressed as the individual's phenotype. In contrast, in females, the recessive trait will be expressed only if it occurs on both X chromosomes. Regardless of whether the child is male or female, the mother must contribute a recessive gene on the X chromosome in order for the trait to be expressed.

Color Blindness Is a Sex-Linked Trait