Final answer:
Xist is an lncRNA that is responsible for the inactivation of one of the two X chromosomes in females during embryonic development. It acts as an inhibitor of eukaryotic gene expression by inducing epigenetic changes to the chromatin.
Step-by-step explanation:
Xist is an lncRNA (long noncoding RNA) that is responsible for the inactivation of one of the two X chromosomes in females during embryonic development. The inactivation of the X chromosome occurs through epigenetic changes to the chromatin. These changes include modifications such as DNA methylation and histone modifications, which lead to gene silencing. Therefore, Xist can be considered as an inhibitor of eukaryotic gene expression.