You're correct in that this is not what the paper is talking about. However, there is a third layer (at least) beyond the gene-coding, most-studied area, and th

You're correct in that this is not what the paper is talking about. However, there is a third layer (at least) beyond the gene-coding, most-studied area, and the article submitted; epigenetics studies how gene expression is modified by histone modification and DNA methylation, basically different ways of switching gene expression on/off or changing the amount of protein made from a certain gene.