diploid

adjective

(Gr. diploos: double; eidos: form) A condition in which the chromosomes in the nucleus of a cell exist as pairs. Each member of the pair carries information about the same genetic characters as the other. Such a pair of chromosomes is referred to as a homologous pair. One of each pair is inherited from each parent. The diploid number of chromosomes in a cell is expressed as 2n. In humans the diploid number is 46, and all body cells contain 46 chromosomes, with the exception of red blood cells, which have no nucleus. Such a diploid number is constant within a species. When gametes are formed the diploid number is reduced by half to the haploid number (n) by meiosis. When gametes fuse at fertilization the diploid condition is restored. Cf. haploid, polyploid.