Set of human chromosomes, coloured scanning election micrograph (SEM). Chromosomes are a packaged form of the genetic material deoxyribonucleic acid (DNA). The DNA condenses into chromosomes during cell replication for ease of division and transport into the new cell. A complete set of chromosomes is known as a karyotype. In humans, there are 46 chromosomes, consisting of 23 pairs. Pair 23 is the sex chromosomes, either xx for females or xy for males.
