Dosage compensation

Dosage compensation

Dosage compensation, also known as Ohno's Hypothesis, is a hypothetical genetic regulatory mechanism which operates to equalize the phenotypic expression of characteristics determined by genes on the X chromosome so that they are equally expressed in the human XY male and the XX female. In 2006, literature was in support of this hypothesis. More recently (2008, 2011), the general consensus in literature refutes this hypothesis.

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Older Research (May no longer be valid)

Dosage compensation may occur in other organisms like the fruit fly Drosophila melanogaster and the round worm Caenorhabditis elegans.

Species can have different mechanisms of dosage compensation. In human females (XX), one chromosome is inactivated (see X-inactivation), resulting in a heterochromatic and largely genetically inactive Barr body. Drosophila males (XY) double the expression of genes along the X chromosome. In C. elegans hermaphrodites (XX), both X chromosomes are partially repressed. Any of these mechanisms results in balancing the relative gene expression between males and females (or, in the case of C. elegans, hermaphrodites and males).

In plants (which lack dimorphic sex chromosomes), dosage compensation can occur when aberrant meiotic events or mutations result in either aneuploidy or polyploidy. Genes on the affected chromosome may be upregulated or down-regulated to compensate for the change in the normal number of chromosomes present.

In Humans*: Women with two normal X chromosomes have the same blood levels of X-chromosome protein products, such as factor VIII, as normal men, who of course have only one X chromosome. An exception to this phenomenon of dosage compensation is the level of steroid sulfatase in blood, which is increased in women compared with men. Not surprisingly it has been shown that the locus for steroid sulfatase (deficiency of which causes a skin disorder known as ichthyosis) is in the pseudoautosomal region.

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  • dosage compensation — dosage compensation. См. компенсация дозы [генов]. (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.

  • dosage compensation — n the genetic mechanism by which the same effect on the phenotype is produced by a pair of identical sex linked genes in the sex (as the human female) having the two sex chromosomes of the same type as by a single gene in the sex (as the human… …   Medical dictionary

  • dosage compensation — Genetic mechanisms that allow genes to be expressed at a similar level irrespective of the number of copies at which they are present. Usually invoked for genes that lie on sex chromosomes, that are thus present in different copy numbers in males …   Dictionary of molecular biology

  • dosage compensation — A regulatory mechanism for sex linked genes, to allow equivalent levels of gene expression from (in mammals) XY or XX genotypes, even though the gene copy number in XX is double that in XY. See: sex linkage, Barr body …   Glossary of Biotechnology

  • dosage compensation — noun : the genetic mechanism by which the same effect on the phenotype is produced by a pair of identical sex linked genes in the sex (as the human female) having the two sex chromosomes of the same type as by a single sex linked gene in the sex… …   Useful english dictionary

  • autosomal dosage compensation — autosomal dosage compensation. См. аутосомная компенсация дозы [гена]. (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.

  • compensation — 1. A process in which a tendency for a change in a given direction is counteracted by another change so that the original change is not evident. 2. An unconscious mechanism by which one tries to make up for fancied or real deficiencies. [L. com… …   Medical dictionary

  • 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.

  • Drosophila roX RNA — Drosophila roX1 ncRNA Conserved secondary structure of roX1 RNA Identifiers Symbol roX1 Rfam …   Wikipedia

  • X-inactivation — The Barr body is indicated by the arrow, it identifies the inactive X (Xi).] macroH2A1 staining. Arrow points to sex chromatin in DAPI stained cell nucleus, and to the corresponding sex chromatin site in the histone macroH2A1 staining.] X… …   Wikipedia

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