XIST (X-inactive specific transcript) is a gene located on the X chromosome that plays a critical role in the process of X-chromosome inactivation (XCI). This process is essential for dosage compensation, ensuring that females (who have two X chromosomes) and males (who have one X chromosome) have similar levels of X-linked gene expression. The XIST gene produces a long non-coding RNA that coats one of the X chromosomes in females, leading to its inactivation.