Color enhanced micrograph of normal, human male chromosomes. This karyotype shows the 46 chromosomes found in most cell nuclei in a man's body. There are 22 pairs of chromosomes and also the gender determining pair. In men, this comprises one X and one Y chromosome (bottom and top respectively). In women, it is made up of two X chromosomes. The Y chromosome carries genetic information responsible for the development of male characteristics. Chromosomes carry genetic information in the form of genes, lengths of DNA that act as recipes for proteins. Karyotypes are an arrangement of chromosomes based on their appearance under a light microscope.