What are sex linked traits? Which of the two definitions of `sex-linked trait` is correct? * Traits controlled by genes present on the non-homologous region of sex chromosomes are called sex-linked traits. * Bodily traits controlled by genes present on the non-homologous regions of sex chromosomes are called sex-linked traits. Here by bodily traits I mean traits that are not involved with sex of an organism. I read the first definition in the book Competition Science Visionand also from Instant notes genetics (page 163). The following is an excerpt from the latter > Sex linkage is not displayed by genes which map to a small segment of X chromosome, the pseudoautosomal region, the part of X chromosome that pairs with Y chromosome in meiosis. The second definition is made up but sounds potentially intuitive to me.

The first definition is correct.

_A sex-linked trait is a trait affected by a locus on a sex chromosome._

If you google sex-linked trait, you will find this same definition (not the exact same words) over and over again.

The definition of sex-linked trait is NOT restricted to traits that are not unrelated to primary or secondary sexual organs. Any phenotypic trait can be sex-linked as long as the causal locus is on a sexual chromosome.