Figure 1 An X-Y plot of two harmonically related sine waves the ratio of the number of horizontal peaks to the number of vertical peaks shows the frequency ratio of the inputs in this case 2 to 5..

Although, in general, females carry two X sex chromosomes in each body cell and males carry one X and one Y, there is some natural variation in the number of sex chromosomes people carry.

The Y chromosomes in many mammals, including us, have been shrinking over tens of millions of years and could eventually disappear, says Kuroiwa. The spiny rat shows how this might happen, she says.

The X and Y chromosomes, commonly referred to as the sex chromosomes, are one such pair. They determine the biological sex, reproductive organs, and sexual characteristics that develop in a person.

Females have two X chromosomes (XX), and males have one X and one Y chromosome (XY). Disorders caused by chromosomal abnormalities can be either numerical or structural.