Xistential crisis: Discovery shows there's more to the story in silencing X chromosomes

Nearly every girl and woman on Earth carries two X chromosomes in nearly every one of her cells -- but one of them does (mostly) nothing. That's because it's been silenced, keeping most of its DNA locked up and unread like a book in a cage. Scientists thought they had figured out how cells do this, but a new piece of research shows the answer isn't quite that clear.