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Xist is an RNA gene on the X chromosome of the placental mammals that acts as major effector of the X inactivation process.

The Xist RNA, a large (18 kb) transcript, is expressed on the inactive chromosome and not on the active one. It is processed similarly to mRNAs, through splicing and polyadenylation, however, it remains untranslated. It has been suggested that this RNA gene evolved at least partly from a protein coding gene that became a pseudogene.[1]

The inactive X is coated with this transcript, which is essential for the inactivation. X lacking Xist will not be inactivated, while duplication of the Xist gene on another chromosome causes inactivation of that chromosome.


  1. ^ Duret L, Chureau C, Samain S, Weissenbach J, Avner P (2006). "The Xist RNA gene evolved in eutherians by pseudogenization of a protein-coding gene". Science 312 (5780): 1653-5. doi:10.1126/science.1126316. PMID 16778056.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Xist". A list of authors is available in Wikipedia.
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