Question

Colorblindness is a sex-linked X-linked recessive trait. A normal woman marries a color-blind man. They have a color-blind daughter. What are the genotypes of all three people?

Answer 1

Answer

Colorblindness is a sex linked X linked recessive trait.

For female to be colorblind then both the X chromosomes has to carry color blind allele. Normal female can be carrier too means only one X chromosome carries color blind allele.

For male to be colorblind, only one color blind allele is sufficient to have color blind male.

C (capital) : color blind allele and c (small) is normal allele

Gentotype of female: XcXC (C is color blind allele and c is normal allele)

Genotype of male: XCY (Y chromosome does not carry color blind allele means only one colorblind allele is sufficient to have color blind male).

Genotype of colorblind daughter : XCXC (Both X chromosome has to carry for female to be color blind)

Female genotype (XcXC): Gametes: Xc or XC

Male genotype (XCY) : Gametes: XC or Y

	Xc	XC
XC	XcXC (carrier female)	XCXC (color blind female)
Y	XcY (Normal male)	XCY (Color blind male)