Histone Acetylation, DNA Methylation and Epigenetics
There may be another method used to affect gene expression that I'm forgetting.
My point is that controlling the expression of what is inherited is not some separate outside thing to what is inherited, neither is methylation outside the DNA double helix - but inside where the bases pair bond to keep the two phosphate backbones together.
Methylated DNA is more attracted to deAcetylated Histones - the two are listed together for a reason.
To activate a gene inactivated through epigenetic, the signal activated proteins Acetylate the Histones bound to DNA before they can get to the methylated DNA, that can then be demethylated and expressed - until the signal to methylate it and deacetylate histones is given and the DNA is wrapped up again - unreadable because it is unreachable by RNA polymerase that might - with the correct transcription factors - express its signal.
The mutation in some human populations that ensures lactose tolerance into adulthood is a mutation in the DNA element to signal to wrap up the lactose gene after weaning that is present in all mammals.
There is - within DNA - the proper sequences to react to changes and pass on reproductive cells with particular DNA configurations of being ‘open’ or ‘closed’ that we call epigenetic. It is DNA that is coding for and reacting with the signals it receives to adopt the proper epigenetic configuration of ‘open’ and ‘closed’ DNA.