Page "Barr body" Paragraph 7

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 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.