Ancestral Eukaryotes Reproduced Asexually, Facilitated by Polyploidy: A Hypothesis. 2019

Sutherland K Maciver
Centre for Discovery Brain Sciences, Edinburgh Medical School, Biomedical Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, Scotland, UK.

The notion that eukaryotes are ancestrally sexual has been gaining attention. This idea comes in part from the discovery of sets of "meiosis-specific genes" in the genomes of protists. The existence of these genes has persuaded many that these organisms may be engaging in sex, even though this has gone undetected. The involvement of sex in protists is supported by the view that asexual reproduction results in the accumulation of mutations that would inevitably result in the decline and extinction of such lineages. It is argued that this phenomenon can be obviated by polyploidy and that the "meiosis-specific genes" are used in other processes, including polyploidy control and homologous recombination, independent of meiosis. These phenomena account for the finding that these genes are expressed in cultures devoid of apparent cell fusion events. Hence, it is also proposed that asexual, and not sexual, reproduction is the ancestral condition.

UI MeSH Term Description Entries
D008540 Meiosis A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells. M Phase, Meiotic,Meiotic M Phase,M Phases, Meiotic,Meioses,Meiotic M Phases,Phase, Meiotic M,Phases, Meiotic M
D011123 Polyploidy The chromosomal constitution of a cell containing multiples of the normal number of CHROMOSOMES; includes triploidy (symbol: 3N), tetraploidy (symbol: 4N), etc. Polyploid,Polyploid Cell,Cell, Polyploid,Cells, Polyploid,Polyploid Cells,Polyploidies,Polyploids
D012100 Reproduction, Asexual Reproduction without fusion of two types of cells, mostly found in ALGAE; FUNGI; and PLANTS. Asexual reproduction occurs in several ways, such as budding, fission, or splitting from "parent" cells. Only few groups of ANIMALS reproduce asexually or unisexually (PARTHENOGENESIS). Asexual Reproduction,Asexual Reproductions,Reproductions, Asexual
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D056890 Eukaryota One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista. Eukaryotes,Eucarya,Eukarya,Eukaryotas,Eukaryote

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