Which is true of sex-linked genes?
they are important only in sex determination.
they may be on one sex chromosome and not the other.
they always produce traits that are codominant.
they always represent recessively inherited disorders.

The true statement is that they may be on one sex chromosome and not the other.

Explanation:

The first statement says that, they are important only in sex determination. But it is not so, as they carry other genes which are not involved in sex determination. They always don’t produce that are co-dominant. It is because when X genes are inherited it exerts certain traits whereas when Y genes are inherited it exerts certain traits which are separate and different in nature. They represent the sex of the individual as well as the disorders associated with it. Thus the statement which states that sex linked genes are inherited on either X-chromosome or on Y-chromosome is inferred as correct statement.