[pvnick]

Well, yeah, if what he's talking about are nucleotide bases, it takes three of them to make a codon. So if you have a sequence ABCABC, then ABC might be a codon (which codes for an amino acid, like a "bead" in a necklace that makes up a protein), BCA might be a codon, and CAB might be a codon. Then at the same time you could go backwards. So really there's six potential different codons that a single basepair might be involved in. But that's probably not what this paper is talking about.

[kissickas]

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.