from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The haploid nucleus of a sperm or egg before fusion of the nuclei in fertilization.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Either of the two haploid nuclei (of a sperm and ovum) that fuse during fertilization
from the GNU version of the Collaborative International Dictionary of English
- n. One of the two bodies or nuclei (called male and female pronuclei) which unite to form the first segmentation nucleus of an impregnated ovum.
from The Century Dictionary and Cyclopedia
- n. 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.
- n. In botany, the nucleus of a conjugating gamete, which on coalescing with another pronucleus forms the germ-nucleus.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote
Sorry, no etymologies found.
In the process a pronucleus is formed which then combines with the female pronucleus.
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.
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.
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_).
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).
-- Completion of the process of extrusion of the chromatic material; _fn_ shows the two chromosomes retained in the egg forming the female pronucleus.
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_).
In this way the centrosome approaches the female pronucleus, and thus finally the two nucleii are brought into close proximity.
Now the centrosome, which is beside the male pronucleus, shows signs of activity.
The nucleus of the mature ovum is termed the female pronucleus.
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