Question

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? [As Canvas cannot depict superscripts in the answer fields, the allele designation, C or c, follows the designation of the chromosome where it is found, so instead of XCXc the answers contain XCXc.] Group of answer choices XCXC and XcY XCXc and XCY XcXc and XCY XcXc and XcY XCXC and XCY

Answer 1

The genotypes of the parents with a color-blind son are XCXc for the mother and XCY for the father. This is because red-green color blindness is a sex-linked recessive trait, and the mother must be a carrier for the son to express the trait.

Step-by-step explanation:

Genotypes of Parents with a Color-Blind Son

Red-green color blindness is a sex-linked recessive trait. This means that males (XY) only need one copy of the recessive allele to express the trait, while females (XX) would need two copies. Given that both parents have normal color vision but have a color-blind son, the mother must be a carrier of the trait and the father must have normal vision. Therefore, the genotypes of the parents must be XCXc for the mother and XCY for the father.

Since the son is color-blind, he has received the X chromosome carrying the color-blindness allele (Xc) from his mother and the Y chromosome from his father. The presence of the recessive allele (Xc) on his single X chromosome leads to him being color-blind. His mother, being a carrier, must have one normal allele (XC) and one color-blind allele (Xc), while his father, with normal color vision, must have the normal allele (XC) on his X chromosome and the Y chromosome that does not carry this trait.