Scientists at Emory University in Atlanta trained male mice to fear the smell of cherry blossom by pairing the smell with a small electric shock. Researchers have already shown that certain fears might be inherited through generations, at least in animals. It’s fine-tuning the way your genes respond to the world.” Can you inherit a memory of trauma? What we’re getting here is the very beginnings of a understanding of how one generation responds to the experiences of the previous generation. “Yehuda’s paper makes some useful progress. The impact of Holocaust survival on the next generation has been investigated for years - the challenge has been to show intergenerational effects are not just transmitted by social influences from the parents or regular genetic inheritance, said Marcus Pembrey, emeritus professor of paediatric genetics at University College London. It’s certainly an opportunity to learn a lot of important things about how we adapt to our environment and how we might pass on environmental resilience.” Whether the gene in question is switched on or off could have a tremendous impact on how much stress hormone is made and how we cope with stress, said Yehuda. It’s not clear whether the gene changes found in the study would permanently affect the children’s health, nor do the results upend any of our theories of evolution. However, research by Azim Surani at Cambridge University and colleagues, has recently shown that some epigenetic tags escape the cleaning process at fertilisation, slipping through the net. Genetic information in sperm and eggs is not supposed to be affected by the environment - any epigenetic tags on DNA had been thought to be wiped clean soon after fertilisation occurs. It’s still not clear how these tags might be passed from parent to child. “To our knowledge, this provides the first demonstration of transmission of pre-conception stress effects resulting in epigenetic changes in both the exposed parents and their offspring in humans,” said Yehuda, whose work was published in Biological Psychiatry. Through further genetic analysis, the team ruled out the possibility that the epigenetic changes were a result of trauma that the children had experienced themselves. View image in fullscreen Children in the Auschwitz-Birkenau concentration camp. They found epigenetic tags on the very same part of this gene in both the Holocaust survivors and their offspring, the same correlation was not found in any of the control group and their children. “If there’s a transmitted effect of trauma, it would be in a stress-related gene that shapes the way we cope with our environment.” “It makes sense to look at this gene,” said Yehuda. The team were specifically interested in one region of a gene associated with the regulation of stress hormones, which is known to be affected by trauma. Likewise, another study has showed that men who smoked before puberty fathered heavier sons than those who smoked after. For example, girls born to Dutch women who were pregnant during a severe famine at the end of the second world war had an above-average risk of developing schizophrenia. Other studies have proposed a more tentative connection between one generation’s experience and the next. Recent studies suggest that some of these tags might somehow be passed through generations, meaning our environment could have and impact on our children’s health. However, our genes are modified by the environment all the time, through chemical tags that attach themselves to our DNA, switching genes on and off. The idea is controversial, as scientific convention states that genes contained in DNA are the only way to transmit biological information between generations. Her team’s work is the clearest example in humans of the transmission of trauma to a child via what is called “epigenetic inheritance” - the idea that environmental influences such as smoking, diet and stress can affect the genes of your children and possibly even grandchildren.
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