the discoveries in epigenetic are rewriting the rules of identity and heredity - also diseases.
the first experience was with agouti mice. They're yellow, fat and prone to diabetes and cancer. In this experiment they changed the mother diet, and the offsprings were slim, brownish and not as prone to cancer and diabetes. That has been achieved only by changing the diet of the mother not by altering the DNA of the mice.
Also epigenetic proved that our DNA can modify itself all along life, depending on our environment. Our DNA is not set in stone.
An other point that I found extremely interesting is that our experiences are also transmitted to the next generation. One example was a woman raped by a member of her family, having the child from the rape. Analyzing the DNA of the raped woman, her mother and her child, the researchers found ''scars'' from the trauma on certain genes, the grand mother and the mother had them, but the most surprising thing is that the child who didn't knew about the rape had the biggest genetic scar.
Therefor our own attitude toward life and negativity will affect our DNA and our offsprings DNA.
I am just starting to look into that field, it is very recent, it is absolutely fascinating, how malleable is our DNA and how everything we do, everything we experience is actually modifying it.