Linha germinal

Watsonia meriana, um exemplo de apomítico.

Em biologia e genética, a linha germinal de um organismo multicelular é a população de células corporais que se diferenciam ou são segregadas no processo usual de reprodução e podem transmitir o seu material genético à progênie[1] As células da linhagem germinativa são denominadas células germinais.[2] Por exemplo, nos animais as células germinais são os gâmetas como os espermatozoides e óvulos e as células das quais derivam. Portanto, são células germinais os gametócitos (ovócito, espermatócito), que produzem os gâmetas, e as células que produzem os gametócitos, chamadas gametogonias (espermatogonia, ovogonia).[2] Nos organismos com reprodução sexual, as células que não constituem parte da linhagem germinativa são denominadas células somáticas.

Por norma, o modo de transmissão do material genético é um processo de reprodução sexual; tipicamente é um processo que inclui alterações sistemáticas no material genético, que dão-se durante a recombinação, meiose e fecundação ou singamia, por exemplo. Porém, existem excepções, como várias formas de apomixia, autogamia, automixia, clonagem, ou partenogénese.[3][4]

As mutações, recombinações ou outras alterações genéticas na linha germinativa podem transmitir-se à prole, enquanto que os alterações nas células somáticas não.[5] Isto não se aplica necessariamente a organismos que se reproduzem de modo somático, como as esponjas[6] e muitas plantas. Por exemplo, uma ampla variedade de Citrus,[7] de Rosaceae e dalgumas Asteraceae, como as Taraxacum produzem sementes por apomixia quando células somáticas diploides deslocam o óvulo ou o embrião ainda prematuro.[8]

O termo linha germinal pode ser também utilizado para indicar a linhagem de células ao longo de muitas gerações de indivíduos, por exemplo, a linha germinal que liga qualquer indivíduo com o seu hipotético último ancestral comum, do qual todos descendem.

Ver também

Referências

  1. ↑ Pieter Dirk Nieuwkoop; Lien A. Sutasurya (1979). Primordial Germ Cells in the Chordates: Embryogenesis and Phylogenesis. [S.l.]: CUP Archive. ISBN 978-0-521-22303-4 
  2. ↑ a b Nikolas Zagris; Anne Marie Duprat; Antony Durston (30 de novembro de 1995). Organization of the Early Vertebrate Embryo. [S.l.]: Springer. pp. 2–. ISBN 978-0-306-45132-4 
  3. ↑ Juan J. Tarin; Antonio Cano (14 de setembro de 2000). Fertilization in Protozoa and Metazoan Animals: Cellular and Molecular Aspects. [S.l.]: Springer. ISBN 978-3-540-67093-3 
  4. ↑ Andrew Lowe; Stephen Harris; Paul Ashton (1 de abril de 2009). Ecological Genetics: Design, Analysis, and Application. [S.l.]: John Wiley & Sons. pp. 108–. ISBN 978-1-4443-1121-1 
  5. ↑ C.Michael Hogan. 2010. Mutation. ed. E.Monosson and C.J.Cleveland. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC
  6. ↑ Brusca, Richard C.; Brusca, Gary J. (1990). Invertebrates. Sunderland: Sinauer Associates. ISBN 0878930981 
  7. ↑ Akira Wakana and Shunpei Uemoto. Adventive Embryogenesis in Citrus (Rutaceae). II. Postfertilization Development. American Journal of Botany Vol. 75, No. 7 (Jul., 1988), pp. 1033-1047 Published by: Botanical Society of America Article Stable URL: http://www.jstor.org/stable/2443771
  8. ↑ K V Ed Peter (5 de fevereiro de 2009). Basics Of Horticulture. [S.l.]: New India Publishing. pp. 9–. ISBN 978-81-89422-55-4 

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