Germ plasm


Germ plasm

Germ plasm or polar plasm is a zone found in the cytoplasm of the egg cells of some model organisms (such as "Caenorhabditis elegans", "Drosophila melanogaster", "Xenopus laevis"), which contains determinants that will give rise to the germ cell lineage. As the zygote undergoes mitotic divisions the germ plasm is ultimately restricted to a few cells of the embryo, these germ cells then migrate to the gonads.

Germ plasm theory

The germ plasm theory is a hypothesis concerning the ability to become germ cells, which is now proven wrong. [ [http://www.esp.org/books/weismann/germ-plasm/facsimile/title3.html The Germ-Plasm: A Theory of Heredity by August Weismann] ]

The term germ plasm was first used by the German biologist August Weismann (b.1834-d.1914) to describe a component of germ cells that he proposed were responsible for heredity, roughly equatable to our modern understanding of DNA. August Weismann formulated the now defunct germ plasm theory in 1893, in which he stated that the germ plasm was the essential nuclear part of germ cells, that it remained qualitatively unchanged from the zygote (in contrast with somatic cells) and was responsible for heredity. In other words it states that a gene's determination was sealed as it, and each of its offspring received fewer and fewer genes from what he called the "germ plasm." (That there is only a set "amount" of "germ plasm" (what we know as genes) and that it was gradually divided amongst the offspring). Cases such as Dolly (the famous cloned ewe) which, via somatic cell nuclear transfer, proved that adult cells retain a complete--as opposed to Weissman's increasingly determined gradual loss of genetic information--set of information; finally putting Weismann's theory to rest.

Germ plasm

*Germplasm, the collection of genetic resources

References


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  • Germ plasm — (Biol.) See {Plasmogen}, and {Idioplasm}. [1913 Webster] …   The Collaborative International Dictionary of English

  • germ plasm — n 1) germ cells and their precursors serving as the bearers of heredity and being fundamentally independent of other cells 2) the hereditary material of the germ cells: GENES * * * the substance postulated by 19th century biologists (notably… …   Medical dictionary

  • germ plasm — germ plasm. См. зародышевая плазма. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • germ plasm — germ′ plasm n. gen the substance of reproductive cells that contains chromosomes • Etymology: 1885–90 …   From formal English to slang

  • germ plasm — n. the reproductive cells of an organism, particularly that portion of the reproductive cells involved in heredity: cf. SOMATOPLASM …   English World dictionary

  • germ plasm — noun the protoplasm of the germ cells that contains chromosomes and genes • Syn: ↑plasm • Hypernyms: ↑protoplasm, ↑living substance * * * noun 1. : germ cells and their precursors regarded as bearers of hereditary characters and as at all times… …   Useful english dictionary

  • germ plasm — Chromatin Chro ma*tin, n. (Biol.) The deeply staining substance of the nucleus and chromosomes of eukaryotic cells, composed of DNA and basic proteins (such as histones), the DNA of which comprises the predominant physical basis of inheritance.… …   The Collaborative International Dictionary of English

  • germ plasm — gyvulių (paukščių) genofondas statusas Aprobuotas sritis veislininkystė apibrėžtis Vienos žemės ūkio gyvulių (paukščių) rūšies populiacijos palyginti pastovi veislių visuma tam tikru laiku. atitikmenys: angl. gene pool; germ plasm vok. Genetische …   Lithuanian dictionary (lietuvių žodynas)

  • germ plasm — gemalinė plazma statusas T sritis augalininkystė apibrėžtis Paveldimumo medžiaga, susitelkusi ląstelių branduoliuose ir perduodama gemalinių ląstelių kitoms kartoms. atitikmenys: angl. germ plasm; idioplasm rus. зародышевая плазма; идиоплазма… …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • germ plasm — noun The cytoplasm of germ cells Syn: polar plasm …   Wiktionary