Which statement about the Y chromosome is true in humans?

• A. The Y chromosome determines maleness in humans
• B. It carries most genes essential for survival
• C. It is inherited from the father on both sexes
• D. It is identical to the X chromosome

Answer: (A)

In humans, sex is determined by a system of sex chromosomes. The Y chromosome carries the SRY gene, which starts the development of testes and sets the male developmental pathway. So the presence of a Y chromosome leads to maleness, while the absence of a Y (having two Xs) leads to female development. The Y is inherited from the father and is passed to sons only, not to daughters. It is much smaller and contains far fewer genes than the X chromosome, so most genes essential for survival are not on the Y. The X and Y are not identical; they are different chromosomes with only small regions of homology.