» "Haplo" redirects here. For the fictional character, see The Death Gate Cycle.Ploidy's the number of complete sets of chromosomes in a biological cell. In humans, the somatic cells that compose the body are diploid (containing two complete sets of chromosomes, one set derived from each parent), but sex cells (sperm and egg) are haploid. In contrast, tetraploidy (four sets of chromosomes)'s a type of polyploidy and's common in plants, and not uncommon in amphibians, reptiles, and various speci… (More on Diploidy)