Mutant fruit flies have helped solve one of the biggest puzzles in genetics: how the stress of starvation or drug addiction can pass on its ill effects to the sufferer's children and grandchildren. Stress is thought to cause "epigenetic" changes that do not alter the sequence of DNA but leave chemical marks on genes that dictate how active they are.
Previous studies have shown that if mice are stressed for two weeks after birth, their offspring will show signs of depression and anxiety, despite enjoying the usual levels of maternal care. And there is mounting evidence that common health problems including diabetes, obesity, mental illness and even fear could be the result of stress on parents and grandparents. …
"What's really exciting is that this study shows a clear molecular mechanism that responds to stress and results in a change in chromatin state in the germ line," says Moshe Szyf at McGill University in Montreal, Canada. "This is a first, to my knowledge."