parthenogenezis

Parthenogenesis, from Greek para (beside) and genesis (origin), is a form of asexual reproduction in which an embryo develops from an unfertilized egg. In animals, offspring produced by parthenogenesis typically carry only maternal genetic material, without paternal contribution. The term is also used in botany to describe seed formation without fertilization in some species, though the broader concept is often captured by apomixis.

Two major cellular routes underlie parthenogenesis: apomixis and automixis. Apomixis skips meiosis entirely, allowing the egg to develop into a complete individual with genetic material that is nearly identical to the mother. Automixis involves meiosis but restores diploidy, for example by fusing products of meiosis, which increases homozygosity in the offspring and alters genetic diversity.

Parthenogenesis is widespread in invertebrates, including many arthropods, nematodes, and rotifers. In vertebrates it is rare but documented in some reptiles—most notably certain all-female lizard species and the Komodo dragon—and in a few fish species. Birds and mammals show little to no natural parthenogenetic reproduction, largely due to genomic imprinting and developmental constraints that favor biparental development.

Genetic and ecological consequences include reduced genetic diversity among offspring, which can limit adaptability and increase susceptibility to deleterious mutations. However, parthenogenesis can enable rapid population growth and successful colonization when mates are scarce or unavailable.

In humans, natural parthenogenesis does not occur under normal conditions. Research uses parthenogenetic activation to study imprinting and developmental biology, and parthenogenetic embryonic stem cell lines have been derived for scientific investigation.