Question

Why is man unable to pass on a sex-linked gene to his son?

Answer 1

A man is unable to pass on a sex-linked gene to his son because sex-linked genes are usually present on the X chromosome. Since males have one X and one Y chromosome (XY), they pass their Y chromosome to their sons, which determines the son's sex as male, and not the X chromosome. Consequently, any gene located on the father's X chromosome is transmitted only to his daughters and never to his sons. This pattern explains why sex-linked genes are regularly transmitted from mother to son (the mother provides the X chromosome to sons), but never from father to son, because sons inherit the Y chromosome from their father, not the X chromosome carrying the sex-linked gene.