What term best describes a trait controlled by genes on the sex chromosomes?

• A. Nuclear genes
• B. Sex linked genes
• C. Chromosomal genes
• D. Autosome-linked genes

Answer: (B)

Traits controlled by genes on the sex chromosomes are called sex-linked. In organisms with XY sex determination, the sex chromosomes are X and Y, and most sex-linked genes reside on the X chromosome. Because males have only one X, any recessive allele on that chromosome will be expressed in the male, leading to inheritance patterns that differ between males and females (such as color blindness or hemophilia in humans). Nuclear genes is too general since it covers all genes inside the nucleus, not specifically those on the sex chromosomes. Chromosomal genes is vague because it could refer to any gene on any chromosome, not necessarily the sex chromosome. Autosome-linked genes are on autosomes and don’t show the distinct sex-related inheritance pattern.