pronucleusThe nucleus of a sperm or an (egg) prior to fertilization. Sperm and egg cells carry half the number of chromosomes of other nonreproductive cells. When the pronucleus of a sperm fuses with the pronucleus of an egg, their chromosomes combine and become part of a single nucleus in the resulting embryo, containing a full set of chromosomes. Related categories• CELL BIOLOGY• GENETICS AND HEREDITY Source: National Human Genome Research Institute Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History |