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1. the compound nucleus in the fertilized oocyte, formed by conjugation of the nuclei of the oocyte and sperm (female and male pronuclei);
2. the zygote nucleus after it commences the first cleavage division.
the nucleus that results from the fusion of male and female pronuclei in a fertilized ovum. Its formation is the final stage in fertilization and initiates the first cleavage of the zygote. Also called cleavage nucleus.
The cell nucleus of a zygote formed by fusion of the male and female pronuclei.
See also: nucleus