Human female chromosomes. Fluorescence light micr- ograph of the 46 chromosomes from a normal human female. This constitutes the full karyotype, that is the total number of chromosomes found in nearly every cell of the female human body. Each cell contains 22 matched pairs of chromosomes, and one sex-determining pair (bottom right). Female and male karyotypes differ only in the sex pair: male sets would be labelled XY instead of the X pair here. Chromosomes are made up mainly of DNA (deox- yribonucleic acid). They carry genes that determine an individual's characteristics. Magnification unknown.