The gene for a certain syndrome is present on a Y chromosome. A man carries the gene for this syndrome. Which of the following is true about the inheritance pattern of the syndrome? A.) Only his son would have the gene for the syndrome. B.) Only his daughter would have the gene for the syndrome. C.) Both son and daughter would have the gene for the syndrome. D.) Neither son nor daughter would have the gene for the syndrome.

This is because during sexual reproduction (that is, between humans), the mother and father each donate a sex chromosome. The mother can only donate an X chromosome since her sex chromosomes are entirely X chromosomes, and the father can donate either an X or Y chromosome since his sex chromosomes are X and Y. Thus, because a male has the sex chromosomes X and Y whereas a female has the sex chromosome X and X, the male must donate a Y chromosome for a son to be born; otherwise he donates an X chromosome and the baby is female. As you can see, because the gene is on a Y chromosome and the father carries and passes it (only to a son), only his son would have the gene for the syndrome.