Here’s a short version of a long, important story: genes can be modified, during life, and those modifications can be passed on to the next generation (! — until recently this was thought impossible).
Here’s a now-classic example. You may have heard about “maternal licking and grooming” in rats. The amount of this care a mother rat provides her young is associated with a single gene, for a receptor in the stress hormone pathway ( glucocorticoid receptor gene). The licking and grooming itself changes the gene in the rat’s young (“epigenetically”, through a small molecule called a methyl group that attaches directly to the young pup’s DNA for this receptor).
Amazingly, this genetic change is transmitted to the next generation: for example, if mom is a high licking and grooming mom, she can transform a genetically low-licking and grooming female pup from another mom into a high licking and grooming mother.Weaver
If this were also true in humans, it would demonstrate that it is possible to “break the chain” of childhood abuse if that abuse pattern was epigenetically, as well as environmentally, propagated. And indeed, a human correlate has recently been described, showing methylation changes of some genes in individuals with a history of childhood maltreatment. Mehta
(updated 12/2014)