Sex Linked Recessive

∞ generated and posted on 2015.12.28 ∞

Genetic trait that can be readily displayed by both genders but nonetheless occurs much more commonly in males.

A Sex Linked Recessive, or Sex-Linked Recessive, is an allele that is both recessive and, in mammals, is located on the X chromosome; as a result, the likelihood of being paired with the corresponding dominant allele is possible in females (who possess two X chromosomes) but is not possible in males, who possess only one X chromosome.

This happens because male mammals carry only a single X chromosome, upon which the gene in question is coded. Male mammals therefore express whatever allele they happen to carry since there is no second copy that could complement its expression. For example, red-green color blindness in humans.

See also simply sex linkage.

If you buy ice cream of random flavor then you are much more likely to get only vanilla if you buy just one completely randomly chosen flavor (one scoop) than if you buy two completely randomly chosen flavors (two scoops). The odds of getting vanilla in one scoop if it is one in, say, 31 flavors, is 1/31 = 0.03. The odds of getting two vanillas in two scoops, in this example, is 1/31 times 1/31 or 0.001, which is 31-fold lower than is the case with only one scoop. This can be important if you really don't like vanilla but somebody else is arbitrarily picking the flavors!

With red-green color blindness, the odds of failing to get a normal color vision allele, the equivalent of something other than vanilla ice cream, is substantially lower if you order two scoops (diploid, two X chromosomes = female) then if you order only one (haploid, one X chromosome = male). Males thus are much more likely to display red-green color blindness than are females.