Question

X and Y genes code for male and female gender. XX is female and XY is male. Why is XcY color blind, but XcXC not color blind? Can an XcXC female pass the color blind trait to her children?

Answer 1

Color blindness is a disorder that follows a X-linked recessive inheritance pattern. Since it is X-linked, the disorder is passed through the X chromosome. It is recessive, so two affected alleles need to be present in females and only one allele is necessary to cause the disorder in a male because males have only one X chromosome which they aquire it from their mother, whereas females have two X chromosomes, one from mother and one from father. Only when both parents pass the affected allele to their daughter (XcXc), the phenotype will be expressed in a female. When only one allele is passed on from either of the parents, the female will act as a carrier (XCXc). A carrier can pass on the disorder to her offsprings in which males will be expressing the phenotype more than females.