structural:reformatting
Mechanism

It is thought that this constitutes the mechanism of choice, and allows downstream processes to establish the compact state of the Barr body. These changes include histone modifications, such as histone H3 methylation (i.e. H3K27me3 by PRC2 which is recruited by Xist) and histone H2A ubiquitination, as well as direct modification of the DNA itself, via the methylation of CpG sites. These changes help inactivate gene expression on the inactive X-chromosome and to bring about its compaction to form the Barr body. 3D reconstructions and microscopic analyses of the Barr body using chromosome painting have found that it has a smoother and rounder morphology than autosomes and the active X chromosome, though it is similar in size to the latter, suggesting its chromatin is only slightly more condensed.