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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.
In a normal situation, all the cells in an individual will have 46 chromosomes, with one being an X and one a Y or with two Xs. However, sometimes during the early copying processes of DNA replication and cell division, one chromosome can be lost. In 45,X/46,XY, most or all of the Y chromosome is lost in one of the newly created cells.
Turner syndrome, also known as 45,X or 45,X0, is a chromosomal abnormality characterised by a partial or completely missing second X chromosome, [4] [24] [25] giving a chromosomal count of 45, instead of the typical count of 46 chromosomes. [24]
46,XX/46,XY chimeric or mosaic is associated with a wide spectrum of different physical presentations, with cases ranging from having a completely normal male or female phenotype [7] [8] [9] to some cases having ovotesticular syndrome. Due to this variation, genetic testing is the only way to reliably make a diagnosis.
The syndrome is defined by the presence of at least one extra X chromosome in addition to a Y chromosome, yielding a total of 47 or more chromosomes rather than the usual 46. Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally.
46, XX male syndrome, also known as de la Chapelle syndrome In this list, the karyotype is summarized by the number of chromosomes, followed by the sex chromosomes present in each cell. (In the second and third cases the karyotype varies from cell to cell, while in the last three cases, the genotype is normal but the phenotype is not.)
A mysterious illness, which the Africa Centers for Disease Control and Prevention is calling "disease X," has killed at least 31 people — mostly children — in the remote Panzi region of the ...
Trisomy X, also known as triple X syndrome and characterized by the karyotype [note 1] 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females, but is rarely diagnosed; fewer than 10% of those with the condition know they have it.