What is "Sex"?

What is sex? We often hear the terms ‘sex’ and ‘gender’ used interchangeably, when in fact they are fundamentally different. While gender refers to a person’s self-representation as male or female as determined by environment and experience, sex is a biological differentiation. The distinction is defined by the chromosomal complement that dictates an organism’s reproductive organs and functions; in short, whether an individual is genetically female (XX, XO) or genetically male (XY, XXY).