What is a sex chromosome?

A sex chromosome is a chromosome that determines the sex of an individual. In many organisms, including humans, there are typically two types of sex chromosomes: X and Y. The combination of these chromosomes determines an individual’s biological sex. For example, individuals with two X chromosomes are typically female, while those with one X and one Y chromosome are typically male.

This definition encapsulates the role of sex chromosomes in determining not just sex but often also guiding secondary sexual characteristics and reproductive functions. The distinct nature of sex chromosomes is crucial in genetic inheritance patterns, as they can carry genes specifically linked to sex determination.

Other options like a chromosome that is identical in all individuals or a non-sex chromosome do not accurately capture the role of sex chromosomes, which are characterized by their role in sex differentiation. Similarly, a chromosome that does not influence development is misleading, as sex chromosomes are essential in guiding developmental processes related to sex.