Tuesday, August 28, 2007

Germ cell

Germ cell

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A germ cell is part of the germline and is involved in the reproduction of organisms. Germ cells should not be confused with "germs" (pathogens).

Germ cells includes all stages of gametogenesis, i.e. gametogonia, gametocytes, gametids and gametes. By a narrower definition, the term germ cell can also just refer to gametes, which are produced by meiosis of the aforementioned germ cells, but this definition is less precise. Cells that are not part of the germline are somatic cells.

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[edit] Ploidy

Normal human somatic cells are diploid, which means they contain 22 pairs of chromosomes, plus 2 sex chromosomes. If the sex chromosomes are XX then the organism is female and if they are XY then the organism is male. Human germ cells are normally haploid, which means they contain half the chromosomes of somatic cells, or 22 chromosomes and one sex chromosome. Thus when the germ cells unite in fertilization, the cell becomes diploid, and commences embryogenesis.

[edit] Origin

Primordial germ cells are predecessors of germ cells. They migrate to the gonadal ridge, where they form gametogonia, and thus start gametogenesis

[edit] See Also

[edit] References


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