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Turner syndrome (TS), commonly known as 45,X, or 45,XO, [note 1] is a chromosomal disorder in which cells have only one X chromosome or are partially missing an X chromosome (sex chromosome monosomy) leading to the complete or partial deletion of the pseudoautosomal regions (PAR1, PAR2) in the affected X chromosome. [2] [6] [7] Most people have ...
Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human somatic cell having 45 or 47 chromosomes instead of the usual 46. [1] [2] It does not include a difference of one or more complete sets of chromosomes.
In the wake of the establishment of the normal number of human chromosomes, 47,XYY was the last of the common sex chromosome aneuploidies to be discovered, two years after the discoveries of 47,XXY, [27] 45,X [28] and 47,XXX [29] in 1959. Even the much less common 48,XXYY [30] had been discovered in 1960, a year before 47,XYY.
The SRY gene, normally found on the Y chromosome, plays an important role in sex determination by initiating testicular development. In about 80 percent of XX males, the SRY gene is present on one of the X chromosomes. [16] [25] The condition results from an abnormal exchange of genetic material between chromosomes (translocation).
This XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in approximately one in 500 live male births. [4] [13] [36] In mammals with more than one X chromosome, the genes on all but one X chromosome are not expressed; this is known as X inactivation. This happens in XXY males, as well as ...
One of the most common signs of low testosterone is a low drive (aka low libido). You may have less interest in activity or realize you’re not spending as much time thinking about as you used to.
The derivative chromosome 21, which contains only heterochromatin, is lost; thus, the individual only has one copy of the material on the short arm of chromosome 21 (21p), but this appears to have no discernible effect. Individuals with this chromosomal arrangement have 45 chromosomes and are phenotypically normal.
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