<P> 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 the genetic material of the sperm and egg fuse . Sperm and egg cells are haploid , meaning they carry half the number of chromosomes of somatic cells . The male and female pronuclei do n't fuse , although their genetic material does . Instead , their membranes dissolve , leaving no barriers between the male and female chromosomes . Their chromosomes can then combine and become part of a single diploid nucleus in the resulting embryo , containing a full set of chromosomes . </P>
the fusion of the male pronucleus and the female pronucleus results in development of
single diploid nucleus in the resulting embryo