Definitions
from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun The haploid nucleus of a sperm or egg before fusion of the nuclei in fertilization.
from The Century Dictionary.
- noun A primitive nucleus; the nucleus of an ovum or of a spermatozoön before these have united to form the definitive nucleus of an impregnated ovum.
- noun In botany, the nucleus of a conjugating gamete, which on coalescing with another pronucleus forms the germ-nucleus.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Biol.) One of the two bodies or nuclei (called
male andfemale pronuclei ) which unite to form the first segmentation nucleus of an impregnated ovum.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun Either of the two
haploid nuclei (of asperm andovum ) that fuse duringfertilization
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote
Etymologies
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Examples
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In the process a pronucleus is formed which then combines with the female pronucleus.
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If, however, it takes place before, the male pronucleus simply remains dormant in the egg while the polar cells are being protruded, and not until after that process is concluded does it begin again to show signs of activity which result in the cell union.
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Now the centrosome, which is beside the male pronucleus, shows signs of activity.
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The chromatin material, in both the male and female pronucleus, soon breaks up into a network in which it is no longer possible to see that each contains two chromosomes (Fig. 41).
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In this way the centrosome approaches the female pronucleus, and thus finally the two nucleii are brought into close proximity.
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Close to it lies its centrosomes (Fig. 35, _ce_), and there is thus formed what is known as the _male pronucleus_ (Fig. 35-40, _mn_).
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-- Completion of the process of extrusion of the chromatic material; _fn_ shows the two chromosomes retained in the egg forming the female pronucleus.
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It becomes surrounded by prominent rays to form an aster (Fig. 41, _ce_), and then it begins to move toward the female pronucleus, apparently dragging the male pronucleus after it.
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The tail by which it has been moving is cast off, and the head containing the chromosomes and the centrosome enters the egg, forming what is called the male pronucleus (Figs. 35-38, _mn_).
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The nucleus of the mature ovum is termed the female pronucleus.
bilby commented on the word pronucleus
"Having pierced the yolk, the spermatozoön loses its tail, while its head and connecting piece assume the form of a nucleus containing a cluster of chromosomes. This constitutes the male pronucleus, and associated with it there are a centriole and centrosome."
- Henry Gray, 'Anatomy of the Human Body', 1918.
September 20, 2009