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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.
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.
Females with one affected X chromosome and one normal X chromosome tend to have milder symptoms. Unlike many other types of intellectual disability, the genetics of these conditions are relatively well understood. [2] [3] It has been estimated there are ~200 genes involved in this syndrome; of these ~100 have been identified. [4]
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.
Disorder Chromosome Mutation Angelman syndrome: 15q DCP Canavan disease: 17p Charcot–Marie–Tooth disease: 17p12 [1] Dup Color blindness: X P Cri du chat syndrome: 5 D Cystic fibrosis: 7q P DiGeorge syndrome: 22q D Down syndrome: 21 C Duchenne muscular dystrophy: Xp D Familial hypercholesterolemia: 19 P Haemochromatosis type 1: 6 P ...
Polysomy X may cause mental and developmental retardation and physical malformation. Klinefelter syndrome is an example of human polysomy X with the karyotype 47, XXY. X chromosome polysomies can be inherited from either a single maternal (49, X polysomies) or paternal (48, X polysomies) X chromosome. [18]
The cells of those born male contain an X chromosome and a Y chromosome that make a pair and give instructions on which genes should be expressed in the body, the researchers said.
Some disorders are caused by a mutation on the X chromosome and have X-linked inheritance. Very few disorders are inherited on the Y chromosome or mitochondrial DNA (due to their size). [3] There are well over 6,000 known genetic disorders, [4] and new genetic disorders are constantly being described in medical literature. [5]