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.
Answer
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.
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