Cause
Risk factors for Turner syndrome are not well known. Genetic mosaicism (46,XX/45,X) is most often implicated, alongside nondisjunction (45,X) and partial monosomy (46,XX). Nondisjunctions increase with maternal age, such as for Down syndrome, but that effect is not clear for Turner syndrome. It is also unknown if there is a genetic predisposition present that causes the abnormality, though most researchers and doctors treating Turners women agree that this is highly unlikely. In 75% of cases, the inactivated X chromosome is of paternal origin. There is currently no known cause for Turner syndrome, though there are several theories surrounding the subject. The only solid fact that is known today is that during conception part or all of the second sex chromosome is not transferred to the fetus. In other words, these females do not have Barr bodies, which are those X chromosomes inactivated by the cell.
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