> > Silencing, once established, is stable: the same X chromosome remains inactivated in all subsequent cell generations. As a result, each female is a mosaic o

> > Silencing, once established, is stable: the same X chromosome remains inactivated in all subsequent cell generations. As a result, each female is a mosaic of cells in which either the maternally inherited or the paternally inherited X is silenced. For those curious about it, a visual example of this is tortoiseshell and calico cats. The orange or black in a cat is X linked. A simple, not quite correct, representation of this would be that a male cat can be either XoY or XbY while a female cat can be XoXo, XoXb, XbXb. The XoXb cats are both black and orange and are frozen at the time when one of the chromosomes were silenced. This is known as X-inactivation and the Wikipedia page ( https://en.wikipedia.org/wiki/X-inactivation https://en.wikipedia.org/wiki/X-inactivation ) even has a picture of a tortoiseshell cat.