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Germ plasm
 
 
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Germ plasm or polar plasm is a zone found in the cytoplasm of the egg cells of some model organisms (such as Caenorhabditis elegans
Caenorhabditis elegans

'Caenorhabditis elegans' is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular biology and developmental biology of C....
, Drosophila melanogaster
Drosophila melanogaster

Drosophila melanogaster is a two-winged insect that belongs to the Diptera, the Order of the Fly. The species is commonly known as the Drosophilidae or vinegar fly, and is one of the most commonly used model organisms in biology, including studies in genetics, physiology and Life history theory....
, Xenopus laevis), which contains determinants that will give rise to the germ cell
Germ cell

Germ cells are progenitors of the gametes. These singled-out cells move through the gut to the developing gonads and undergo mitotic Cell proliferation followed by meiosis and Cellular differentiation into either eggs or sperm ....
 lineage. As the zygote undergoes mitotic
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 divisions the germ plasm is ultimately restricted to a few cells of the embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
, these germ cells then migrate to the gonad
Gonad

The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells....
s.

germ plasm theory is a hypothesis concerning the ability to become germ cells, which is now proven wrong.






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Germ plasm or polar plasm is a zone found in the cytoplasm of the egg cells of some model organisms (such as Caenorhabditis elegans
Caenorhabditis elegans

'Caenorhabditis elegans' is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular biology and developmental biology of C....
, Drosophila melanogaster
Drosophila melanogaster

Drosophila melanogaster is a two-winged insect that belongs to the Diptera, the Order of the Fly. The species is commonly known as the Drosophilidae or vinegar fly, and is one of the most commonly used model organisms in biology, including studies in genetics, physiology and Life history theory....
, Xenopus laevis), which contains determinants that will give rise to the germ cell
Germ cell

Germ cells are progenitors of the gametes. These singled-out cells move through the gut to the developing gonads and undergo mitotic Cell proliferation followed by meiosis and Cellular differentiation into either eggs or sperm ....
 lineage. As the zygote undergoes mitotic
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 divisions the germ plasm is ultimately restricted to a few cells of the embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
, these germ cells then migrate to the gonad
Gonad

The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells....
s.

Germ plasm theory

The germ plasm theory is a hypothesis concerning the ability to become germ cells, which is now proven wrong.

The term germ plasm was first used by the German biologist August Weismann (b.1834-d.1914) to describe a component of germ cell
Germ cell

Germ cells are progenitors of the gametes. These singled-out cells move through the gut to the developing gonads and undergo mitotic Cell proliferation followed by meiosis and Cellular differentiation into either eggs or sperm ....
s that he proposed were responsible for heredity
Heredity

Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism....
, roughly equatable to our modern understanding of DNA
DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetics instructions used in the development and functioning of all known living organisms and some viruses....
. 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
Somatic cell nuclear transfer

In genetics and developmental biology, somatic cell nuclear transfer is a laboratory technique for creating a clonal embryo, using an ovum with a donor nucleus ....
, 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
    Germplasm

    A germplasm is a collection of genetic resources for an organism. For plants, the germplasm may be stored as a seed collection or, for trees, in a nursery....
    , the collection of genetic resources