euploidy

Euploidy is the state of having a chromosome number that is an exact multiple of the haploid chromosome complement for a given species. It is distinguished from aneuploidy, where there is an abnormal number of chromosomes that is not a multiple of the haploid set.

For many species, the normal somatic complement is diploid (2n). Euploid variants include haploid (n), triploid (3n), tetraploid (4n) and higher multiples. When euploidy arises from genome duplication within a species it is called autopolyploidy; when it results from hybridization between species it is allopolyploidy. Polyploidy is common in plants and can contribute to speciation and larger cells and organs; in animals it is often associated with developmental abnormalities and reduced fertility, though some lineages tolerate it.

Origin and detection: Polyploidy can result from nondisjunction during meiosis or mitosis or from endoreduplication. It can be detected by karyotyping, flow cytometry, or DNA-based methods. Clinically, most polyploidies in humans are rare and often lethal, while aneuploidies, which involve non-multiples of the haploid set, are more common and associated with developmental disorders.