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'''Germ plasm''' or polar plasm is a zone found in the cytoplasm of the [http://en.wikipedia.org/wiki/Egg_cell egg cells] of some [[model]] [[organisms]] (such as [http://en.wikipedia.org/wiki/Caenorhabditis_elegans Caenorhabditis elegans], [http://en.wikipedia.org/wiki/Drosophila_melanogaster Drosophila melanogaster], [http://en.wikipedia.org/wiki/Xenopus_laevis Xenopus laevis]), which contains determinants that will give rise to the germ cell lineage. As the zygote undergoes [http://en.wikipedia.org/wiki/Mitosis mitotic] divisions the germ plasm is [[ultimately]] restricted to a few [[cells]] of the [http://en.wikipedia.org/wiki/Embryo embryo]. These germ cells then migrate to the [http://en.wikipedia.org/wiki/Gonad gonads].
==Germ plasm theory==
The term germ plasm was first used by the German [[biologist]] [http://en.wikipedia.org/wiki/August_Weismann August Weismann] (1834–1914). His germ plasm [[theory]] states that multicellular [[organisms]] consist of [http://en.wikipedia.org/wiki/Germ_cell germ cells] that contain and transmit heritable [[information]], and somatic cells which carry out ordinary [[bodily]] [[functions]].[1] In the germ plasm [[theory]], [[inheritance]] in a multicellular [[organism]] only takes place by means of the germ cells: the [http://en.wikipedia.org/wiki/Gametes gametes], such as egg cells and sperm cells. Other cells of the [[body]] do not [[function]] as [[agents]] of [[heredity]]. The [[effect]] is one-way: germ cells produce somatic cells, and more germ cells; the germ cells are not affected by anything the somatic cells learn or any [[ability]] the [[body]] acquires during its life. [[Genetic]] [[information]] cannot pass from soma to germ plasm and on to the next [[generation]]. This is referred to as the [http://en.wikipedia.org/wiki/Weismann_barrier Weismann barrier].[2] This [[idea]], if true, rules out the inheritance of acquired characteristics as proposed by [http://en.wikipedia.org/wiki/Jean-Baptiste_Lamarck Jean-Baptiste Lamarck].[3]
The part of Weismann's [[theory]] which proved most vulnerable was his notion that the germ plasm (effectively, [[genes]]) were successively reduced during division of somatic cells. As modern [[genetics]] [[developed]], it became clear that this idea was quite wrong.[4] Cases such as [http://en.wikipedia.org/wiki/Dolly_(sheep) Dolly] (the famous cloned ewe) which, via somatic cell nuclear transfer, proved that adult cells retain a complete set of [[information]] – as opposed to Weismann's increasingly determined [[gradual]] loss of [[genetic]] [[information]] – putting this aspect of Weismann's theory to rest.
==Germplasm, other usage==
* [http://en.wikipedia.org/wiki/Germplasm Germplasm], the [[collection]] of genetic [[resources]]
==References==
# 1892. Das Keimplasma: eine Theorie der Vererbung. Fischer, Jena.
# [http://www.esp.org/books/weismann/germ-plasm/facsimile/ Germ-Plasm, a theory of heredity (1893)- Full online text]
# Huxley, Julian 1942. Evolution, the modern synthesis. p17
# For example, by studies of polytene chromosomes in salivary glands (i.e. somatic cells) of larval Drosophila.
Retrieved from "http://en.wikipedia.org/wiki/Germ_plasm"
'''Germ plasm''' or polar plasm is a zone found in the cytoplasm of the [http://en.wikipedia.org/wiki/Egg_cell egg cells] of some [[model]] [[organisms]] (such as [http://en.wikipedia.org/wiki/Caenorhabditis_elegans Caenorhabditis elegans], [http://en.wikipedia.org/wiki/Drosophila_melanogaster Drosophila melanogaster], [http://en.wikipedia.org/wiki/Xenopus_laevis Xenopus laevis]), which contains determinants that will give rise to the germ cell lineage. As the zygote undergoes [http://en.wikipedia.org/wiki/Mitosis mitotic] divisions the germ plasm is [[ultimately]] restricted to a few [[cells]] of the [http://en.wikipedia.org/wiki/Embryo embryo]. These germ cells then migrate to the [http://en.wikipedia.org/wiki/Gonad gonads].
==Germ plasm theory==
The term germ plasm was first used by the German [[biologist]] [http://en.wikipedia.org/wiki/August_Weismann August Weismann] (1834–1914). His germ plasm [[theory]] states that multicellular [[organisms]] consist of [http://en.wikipedia.org/wiki/Germ_cell germ cells] that contain and transmit heritable [[information]], and somatic cells which carry out ordinary [[bodily]] [[functions]].[1] In the germ plasm [[theory]], [[inheritance]] in a multicellular [[organism]] only takes place by means of the germ cells: the [http://en.wikipedia.org/wiki/Gametes gametes], such as egg cells and sperm cells. Other cells of the [[body]] do not [[function]] as [[agents]] of [[heredity]]. The [[effect]] is one-way: germ cells produce somatic cells, and more germ cells; the germ cells are not affected by anything the somatic cells learn or any [[ability]] the [[body]] acquires during its life. [[Genetic]] [[information]] cannot pass from soma to germ plasm and on to the next [[generation]]. This is referred to as the [http://en.wikipedia.org/wiki/Weismann_barrier Weismann barrier].[2] This [[idea]], if true, rules out the inheritance of acquired characteristics as proposed by [http://en.wikipedia.org/wiki/Jean-Baptiste_Lamarck Jean-Baptiste Lamarck].[3]
The part of Weismann's [[theory]] which proved most vulnerable was his notion that the germ plasm (effectively, [[genes]]) were successively reduced during division of somatic cells. As modern [[genetics]] [[developed]], it became clear that this idea was quite wrong.[4] Cases such as [http://en.wikipedia.org/wiki/Dolly_(sheep) Dolly] (the famous cloned ewe) which, via somatic cell nuclear transfer, proved that adult cells retain a complete set of [[information]] – as opposed to Weismann's increasingly determined [[gradual]] loss of [[genetic]] [[information]] – putting this aspect of Weismann's theory to rest.
==Germplasm, other usage==
* [http://en.wikipedia.org/wiki/Germplasm Germplasm], the [[collection]] of genetic [[resources]]
==References==
# 1892. Das Keimplasma: eine Theorie der Vererbung. Fischer, Jena.
# [http://www.esp.org/books/weismann/germ-plasm/facsimile/ Germ-Plasm, a theory of heredity (1893)- Full online text]
# Huxley, Julian 1942. Evolution, the modern synthesis. p17
# For example, by studies of polytene chromosomes in salivary glands (i.e. somatic cells) of larval Drosophila.
Retrieved from "http://en.wikipedia.org/wiki/Germ_plasm"
