XIST (gene) - Dosage Compensation

Dosage Compensation

X inactivation plays a key role in dosage compensation mechanisms that allow for equal expression of the X and autosomal chromosomes. Different species have different dosage compensation methods, with all of the methods involving the regulation of an X chromosome from one of the either sexes. Some methods involved in dosage compensation to inactive one of the X chromosomes from one of the sexes are Tsix antisense gene, DNA methylation and DNA acetylation; however, the definite mechanism of X inactivation is still poorly understood. If one of the X chromosomes is not inactivated or is partially expressed, it could lead to over expression of the X chromosome and it could be lethal in some cases.

Turner's Syndrome is one example of where dosage compensation does not equally express the X chromosome, and in females one of the X chromosomes is missing or has abnormalities, which leads to physical abnormalities and also gonadal dysfunction in females due to the one missing or abnormal X chromosome. Turner's syndrome is also referred to as a monosomy X condition.