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(cell and molecular biology)
Fusion of gametic nuclei, as in fertilization.



the fusion of the nuclei of gametes into the nucleus of a zygote.

Karyogamy is the essence of fertilization, in which the paired nature of the homologous chromosomes carrying genetic information from the maternal and paternal gametes is restored. Karyogamy may occur immediately after the gametes fuse (for example, in the sea urchin) or, more often, somewhat later, in the metaphase of the first division. In some animals (for example, the water flea), algae, and fungi, the nuclei of the male and female draw together to form a dikaryon.

References in periodicals archive ?
Additionally, it might well be possible that androgenesis would be induced directly over the sperm cell, before fertilization and karyogamy, as described for maize ig1 mutants.
First, a fertilizing sperm takes on a species-specific conformation inside embryos that may serve a role in positioning the male pronucleus before karyogamy (Karr 1991).
1666) found that in obscura group species "as genetic differentiation increases, hybrids are no longer possible; but then oddly at an even greater distance hybrids are again possible!" These authors list three factors that may result in a failure to produce hybrids: (1) sperm are not transferred; (2) interspecific sperm are expelled from the female, and (3) while karyogamy may occur, genomes are incompatible for continued development.