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(cell and molecular biology)
One of the two nuclear bodies of a newly fertilized ovum, the male pronucleus and the female pronucleus, the fusion of which results in the formation of the germinal (cleavage) nucleus.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the haploid nucleus of a sex cell, or gamete. During fertilization, the diploid nucleus of the zygote, or synkaryon, is formed by the fusion of two pronuclei; the chromosome sets of both pronuclei are joined in the synkaryon.

In multicellular organisms and a number of protozoans that are anisogamous, there are female and male pronuclei. The female pronucleus is the nucleus of a mature egg cell, or macro-gamete. The male pronucleus is formed by the swelling of the nucleus of a spermatozoid, or microgamete, after it has become embedded in the cytoplasm of an egg cell. In isogamous unicellular organisms, the fusing pronuclei, like the gametes themselves, are morphologically indistinguishable. During autogamy, pronuclei that have been formed in the same cell fuse; they are usually sister nuclei. During conjugation in infusorians, two pronuclei form in each partner—a stationary pronucleus and a migrating pronucleus. There is first an exchange of migrating pronuclei between partners through a cytoplasmic bridge, which is followed by the fusion of the pronuclei in each of the partners.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Emanating from the MT bundle toward and surrounding the female pronucleus is a prominent cone-shaped array of MTs.
Such radial arrays of microtubules are present in fertilized eggs of a number of animals, including annelids (Astrow et al., 1989), ctenophores (Houliston et al., 1993), echinoderms (Harris et al., 1980), ascidians (Sawada and Schatten, 1988), and amphibians (Houliston and Elinson, 1991; Schroeder and Gard, 1992; Elinson and Palacek, 1993), and are associated with the sperm aster and sometimes with the female pronucleus as well.
Following the completion of the meiotic divisions, the chromatin of the female and male pronuclei begins to decondense and the male pronucleus starts to migrate toward the female pronucleus. The distance a male pronucleus traverses differs in each zygote, because the entry point of sperm is highly variable.

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