I think that a one-word answer would be "epigenetics". Sections of genes are turned on and off by various chemical processes, so that the genes that are activel

I think that a one-word answer would be "epigenetics". Sections of genes are turned on and off by various chemical processes, so that the genes that are actively transcribed into proteins can change without the underlying DNA changing. There was a brief mention of it at the bottom of the article.