Illustration of human X and Y chromosomes. One chromosome of each pair has replicated during cell division to form an identical copy, or chromatid. The chromatids of a pair are joined at the centromere, which divides a chromatid into two asymmetrical regions. Chromosomes are present in the nucleus of every cell of the body. They consist of genetic material, DNA (deoxyribonucleic acid), in association with proteins. Most human cells contain 46 chromosomes, 23 inherited from the mother and 23 from the father.