Aberrations Of Sex Chromosomes At A Glance

In aberrations of sex chromosomes can find a aneuploidy, partial deletions or duplications of the sex chromosomes or a mosaic.

Aberrations of sex chromosomes are common and cause syndromes that involve a large number of congenital and developmental disorders. They are rarely suspected prenatally, but can be discovered during a survey carried out for other reasons karyotyping randomly, such as advanced maternal age. The anomalies are often hard to detect at birth and can sometimes are not diagnosed until puberty.

In aberrations of sex chromosomes can find a aneuploidy, partial deletions or duplications of the sex chromosomes or a mosaic. Aberrations of sex chromosomes are common and cause syndromes that involve a large number of congenital and developmental disorders. They are rarely suspected prenatally, but can be discovered during a survey carried out for other reasons karyotyping randomly, such as advanced maternal age. The anomalies are often hard to detect at birth and can sometimes are not diagnosed until puberty. The effects of the X chromosome abnormalities are not as heavy as the autosomal analog anomalies. Women with three X chromosomes often appear physically and mentally normal and fertile. In contrast, all known trisomies have devastating effects. Similarly, benign is also the absence of an X chromosome, although it (Turner’s syndrome) results in a specific syndrome, while the lack of an autosome runs inevitably fatal. Lyon hypothesis (X-inactivation) with two X chromosomes, women have two places for each X-linked gene, compared to a single location in men. This imbalance seems to require -problem a genetic “dosage”. After the Lyon hypothesis during early embryonic development (around day 16) in each body cell of one of the two X chromosomes of the woman is genetically inactivated. In fact, no matter how many X chromosomes are present, all but one inactivated. Molecular genetic studies have revealed, however, that some genes on the inactivated X chromosome (or chromosomes) do not have a function. These few are important for normal female development. The gene responsible for the inactivation of genes on the X-chromosome is XIST. It produces RNA that triggers inactivation. Whether the maternal or the paternal X chromosome is inactivated, usually takes place in each cell at the time of inactivation by chance, and the same X remains inactive for all derived cells. It follows that all women are mosaics, with some cells an active maternal X chromosome and other active paternal X chromosome carry. Sometimes the running random inactivation of the relatively small number of cells that are present at the time of inactivation leads to the fact that in a specific resulting tissue outweigh active male or active female X chromosomes (so-called. Skewed X-inactivation). This “crooked” X-inactivation may be responsible for X-linked diseases such as hemophilia and muscular dystrophy in heterozygous women manifest themselves occasionally with mild symptoms (if there is a 50: were 50 distribution of active X chromosomes, presumably would all asymptomatic). To such a lopsided inactivation may also be held after inactivation selection.

Health Life Media Team

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