There's the genome and then there is the epigenome. Russell Brandom writes at the Verge that the role of the epigenome in inheritance is increasingly fascinating researchers.
"[T]hese studies are having a profound impact on how scientists look at biological inheritance and pointing the way towards new ways of thinking about our bodies, particularly for inherited factors like obesity or cancer risk," he writes. "Instead of a permanent code, what if your body's data is written in pencil?"
For instance, he notes that mothers who have undergone bariatric surgery had children who were at lower risk of becoming obese, despite their genetics remaining the same. Additionally, a mouse study showed that parents who were conditioned to be afraid of a certain smell passed that fear on their pups, even if the parents weren't around to teach that fear to their offspring. He adds that children of human parents with PTSD have lower levels of stress-response hormomes." What if those stressful experiences are leaving epigenetic markers, passed down from parent to child?" Brandom says.
How this all may work isn't yet clear. "We still don't really understand how experience can create these marks," McGill University's Moshe Szyf tells him. "It's not so easy to find out. But we understand that there are changes."