Remember, we’d done nothing to change the genome. We’d simply broken the mice’s DNA in places where there aren’t any genes and forced the cell to paste, or “ligate,” them back together. Just to make sure, later we broke the DNA in other places, too, with the same results. Those breaks had induced a sirtuin response. When those fixers went to work, their absence from their normal duties and presence on other parts of the genome altered the ways in which lots of genes were being expressed at the wrong time.
