Humans usually have 46 chromosomes in each body cell. These are arranged in 23 pairs. Of these, 22 pairs are called autosomes, and the last pair is made up of the sex chromosomes.
Chromosomes are structures inside cells that carry DNA, which contains genetic information. They help guide how the body grows, works, and passes traits from parents to children. In most females, the sex chromosomes are XX, and in most males, they are XY.
Egg and sperm cells are different from most body cells because they each carry 23 chromosomes. When an egg and sperm join, the baby usually receives 46 chromosomes total. Changes in the number or structure of chromosomes can sometimes lead to genetic conditions.
A chromosome test, often called a karyotype, may be recommended if there are concerns about development, fertility, pregnancy loss, or a suspected genetic condition. A genetic specialist can help explain test results and what they may mean for health or family planning.