"Haplo" redirects here. For the fictional character, see The Death Gate Cycle. Ploidy is the number of homologous sets of chromosomes in a biological cell. The ploidy of cells can vary within an organism. In humans, most cells are diploid (containing one set of chromosomes from each parent), but sex cells (sperm and egg) are haploid. In contrast, tetraploidy (four sets of chromosomes) is a type of polyploidy and is common in plants, and not uncommon in amphibians, reptiles, and various species of insects. The number of chromosomes in one of the mutually-homologous sets is called the monoploid number (x). This is the same number for every set in every cell of a given organism. Euploidy is the state of a cell or organism having an integral multiple of the monoploid number, possibly excluding the sex-determining chromosomes. For example, a human cell has 46 chromosomes, which is an in

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