What is Sex-linked Traits in genetics?

The X-chromosomes carry genes for traits other than sex characteristics. Morgan discovered these sex-linked traits while observing the inheritance of eye color in Drosophila. If a female fly with mutant white eyes is mated with a wild-type male with red eyes, the male offspring are all white-eyed, while the females are red-eyed. If one of the females of the F1 generation is mated to a white-eyed male, about half of the offspring will be red-eyed and half white-eyed, regardless of sex.

The female carries both dominant and recessive genes, and exhibits the dominant phenotype, but half of the female's eggs carry the recessive trait. Moreover, all males carrying this trait will exhibit the recessive phenotype: this is because the Y chromosome carries no corresponding allele, since the Y chromosome is shorter and lacks some genes.

In humans, the gene for colorblindedness is inherited as a recessive sex-linked trait. A female is less often colorblind than a male, because she must be homozygous for the gene to be expressed, whereas the male does not have a corresponding allele to mask the recessive gene for colorblindedness.