(plural, pronuclei) - Refers to the haploid nucleus of egg or sperm prior to fertilization, and immediately after fertilization, before the sperm and egg nuclei have fused into a single diploid nucleus.
the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote
Gr. pro- - a prefix meaning before, in front of; L. nux - nut]. The haploid, or reduced, nucleus of a gamete (ie. sperm and egg). The reduced nuclei of the sperm and egg join together in the fertilized ovum to form the zygote.
The nucleus of a sperm or an egg prior to fertilization.
A pronucleus (plural: pronuclei) is the nucleus of a sperm or an egg cell during the process of fertilization, after the sperm enters the ovum, but before they fuse. Sperm and egg cells are haploid, meaning they carry half the number of chromosomes of somatic (nonreproductive) cells. When the pronucleus of a sperm fuses with the pronucleus of an egg, their chromosomes combine and become part of a single diploid nucleus in the resulting embryo, containing a full set of chromosomes.