Polysomy

Polysomy

Polysomy is a condition in which an organism has at least one more chromosome than normal, i.e. the number of a particular chromosome is not diploid - there may be three or more copies of the chromosome rather than the expected two copies. Polysomy is usually caused by non-disjunction (the failure of a pair of homologous chromosomes to separate) during meiosis, but may also be due to a translocation mutation. Down's syndrome is an example of polysomy where affected individuals possess three copies (trisomy) of chromosome 21.

Polyploidy (in Greek: πολλαπλόν - multiple) is a term applied to cells or organisms that contain more than two copies of each of their chromosomes. Where an organism is normally diploid, some spontaneous aberrations may occur which are usually caused by a hampered cell division. Polyploid types are termed corresponding to the number of chromosome sets in the nucleus: triploid (three sets; 3n), tetraploid (four sets; 4n), pentaploid (five sets; 5n), hexaploid (six sets; 6n) and so on. A haploid (n) only has one set of chromosomes. Haploidy may also occur as a normal stage in an organism's life cycle as in ferns and fungi.


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  • polysomy — polysomy. См. полисомия. (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.

  • polysomy — polisomija statusas T sritis augalininkystė apibrėžtis Vienos ar keleto papildomųjų chromosomų buvimas chromosomų rinkinyje. atitikmenys: angl. polysomy rus. полисомия …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • polysomy — Situation in which all chromosomes are present, and some are present in greater than the diploid number, for example, trisomy 21 …   Dictionary of molecular biology

  • polysomy — State of a cell nucleus in which a specific chromosome is represented more than twice. Cells containing three, four, or five homologous chromosomes are referred to, respectively, as trisomic, tetrasomic, or pentasomic. Cf.:polyploidy. [poly + G.… …   Medical dictionary

  • polysomy — poly·so·my …   English syllables

  • polysomy — noun congenital defect of having one or more extra chromosomes in somatic cells • Hypernyms: ↑birth defect, ↑congenital anomaly, ↑congenital defect, ↑congenital disorder, ↑congenital abnormality …   Useful english dictionary

  • полисомия — polysomy полисомия. Увеличение группы гомологичных хромосом за счет появления избыточных хромосом (третьей, четвертой и т.д. соответственно, трисомия, тетрасомия и т.п.), в основе П. неправильное расхождение хромосом в анафазе клеточных делений.… …   Молекулярная биология и генетика. Толковый словарь.

  • polysomic — Pertaining to or characterized by polysomy. * * * poly·so·mic .päl i sō mik adj basically polyploid but having one or a few chromosomes present in a greater or smaller number than is characteristic of the rest of the chromosome complement… …   Medical dictionary

  • Y chromosome — Human Y chromatid The Y chromosome is one of the two sex determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 …   Wikipedia

  • компенсация дозы [генов] — dosage compensation компенсация дозы [генов]. Mеханизм регуляции экспрессии генов, сцепленных с полом; при механизме определения пола ХХ ХY у самок К.д. связана с инактивацией одной из Х хромосом <X inactivation> (при полисомии… …   Молекулярная биология и генетика. Толковый словарь.

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