noun (plural pronuclei /-klēˌī/)Biology
Either of a pair of gametic nuclei, in the stage following meiosis but before their fusion leads to the formation of the nucleus of the zygote.
- In normal fertilisation the formation of male and female pronuclei is an important stage just before the maternal and paternal chromosomes start to pair up in preparation for the first cell division.
- The sperm and egg pronuclei form the zygotic nucleus.
- Diploid zygotes created by combining a male and a female pronucleus gave rise to viable embryos, but combining two male or two female pronuclei did not.
- Example sentences
- Arrowheads point to sister chromatids and refer to chromosome replication during the pronuclear stage.
- In mice and humans, the pronuclear membranes disappear before the pronuclei come together.
- In contrast, wisp embryos arrest after completion of meiosis II, before pronuclear fusion.
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