X-Inactivation
Mosaic cell view
Inactivation process
XIST RNA coating
Re-randomize cells
Calico cat example
X Chromosome Inactivation
Female mammals silence one X chromosome randomly in each cell (Lyon hypothesis). XIST lncRNA coats and silences one X, forming the Barr body. This creates a mosaic organism — like a calico cat.
Paternal X active
Maternal X active
Inactive X (Barr body)
XIST RNA
H3K27me3 repression
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Calico cat
X-inactivation mosaic