Egg Cell


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.

Egg Cell

 

(also ovicell), in plants, the female sex cell; the relatively large nonmotile cell that is the parent cell of a new organism. The egg cell occurs in all higher plants and in certain algae and fungi (in oogamous species it is formed in the oogonia). In bryophytes, Lycopodiales, and gymnosperms the egg cell originates in the archegonia; in angiosperms it is a component of the egg apparatus of the embryo sac.

The shape and size of the egg cell vary in different plants. The egg cell is considerably larger than the sperm. There is a vacuole in the upper part. An external cellulose membrane is absent. There is, however, a thin plasma membrane, which promotes the exchange of matter between the egg cell and the cytoplasm of the embryo sac surrounding it. The plasma membrane also facilitates penetration by the sperm during fertilization, after which the zygote develops a typical external egg membrane.

The egg cell has marked morphological and physiological polarity, which is manifested in the varied activity of metabolism. Physiological activity is higher in the upper part of the cell than in the lower. The fertilized egg cell forms the zygote, from which the embryo develops. The cytoplasm of the egg cell contains organelles and inclusions characteristic also of other cells (mitochondria, leucoplasts, chloroplasts, chromoplasts).

REFERENCES

Gerasimova-Havashina, E. N. “Pyl’tsevoe zerno, gamety i polovoi protsess u pokrytosemennykh.” Trudy Botanicheskogo instituia. Morfologiia i anatomiia rastenii, 1951, issue 2.
Iakovlev, M. S. “Gametogenez, zarodyshevyi meshok i pyl’tsevoe zerno.” Botanicheskii zhurnal, 1974, vol. 59, no. 12.
Poddubnaia-Arnol’di, V. A. Tsitoembriologiia pokrytosemennykh rastenii. Moscow, 1976.
References in periodicals archive ?
These patents and patent applications represent some of the earliest filings on advanced cellular reprogramming technologies that do not utilize egg cells in the traditional sense of somatic cell nuclear transfer," remarked William Caldwell, Chief Executive Officer of ACT.
King transplant a nucleus of a frog embryo cell into an unfertilized egg cell with the nucleus removed.
One might argue that there is no new soul in the egg cell donated by a woman.
When the first sperm encounters the egg cell, the outer membranes of the sperm and egg fuse, and chemical changes in the egg rapidly prevent any more sperm from entering.
Scientists have mixed ear of a rat and egg cell of a cow, and likewise any organ of any living being and the egg cell of a cow.
Using an electric current, they fused the enucleated egg cell with a cell from the udder tissue.
The science is simple -- replace the nucleus of an egg cell with a nucleus containing the DNA from any of the millions of body cells of an individual -- to produce an embryo leading to a normal birth of an individual that is a clone of the original "parent.
Egg cells must be activated for SCNT to be successful.
In this study, the researchers removed the nucleus of an unfertilized egg cell and replaced it with the nucleus of another donor's egg cell.
He replaced the immature cell nucleus in an egg cell of a frog with the nucleus from a mature intestinal cell.
Tilly's group convincingly shows that stem cells in human ovaries can make egg cell precursors, says Evelyn Telfer of the University of Edinburgh.
The fertilized egg cell begins to divide and grow to become a blastocyst (ball of about 100 cells), then an embryo, and finally a fetus (unborn animal eight weeks after fertilization).