Eh I disagree. It's been known for a while that you need something other than just DNA to get the heterogeneity of cellular phenotypes. Remember that your Iris

Eh I disagree. It's been known for a while that you need something other than just DNA to get the heterogeneity of cellular phenotypes. Remember that your Iris and toenails have the same DNA, yet wildly different gene expression profiles. Without cellular memory that would be impossible and we would all still be single celled organisms :)