A trait controlled by a gene on the sex chromosome is known as a sex-linked trait.

Here's why:

* Sex Chromosomes: These are the chromosomes that determine an individual's sex (e.g., XX for female, XY for male in humans).

* Genes on Sex Chromosomes: These genes are responsible for traits related to sexual development as well as other characteristics.

* Inheritance: Sex-linked traits are inherited differently from traits controlled by genes on other chromosomes (autosomes) because of the unequal number of sex chromosomes in males and females.

Let me know if you'd like more information about sex-linked traits, like examples of common ones!