that is really what i have been , howested in in the study, that regulation worth best works in the dna. >> when you say it dnas expressed in who we are, in cells, what sort of things are determined by our dna, and what sort of things are sort of just guided by our dna, but are not completely determined by it #dr. doudna: that is the $64,000 question. [laughter] walter: yes? people have been trying to understand the code of dna, what the genes are that make up a human being for example, and one of the great, i think it is great, things that come out of that, is that it is complicated, right? it is really come get it. it is not just a list of genes, but in fact, there are many layers to the way that the information is used. i think that what you are alluding to is something called at the genetics, which really means making chemical changes to dna, that do not alter the genes themselves, that change the way that the information is actually used. : can you give us an example of something that is epigenetic, meaning that it is controlled by the environment, and what is purely genetic and en