"Pregnant women are to be treated well," I recall my friend telling me. "How well?" I asked. He said while a woman is pregnant, she should be unburdened by any psychological or physical troubles. He was quite serious as he told me. He said that so long as the mother is happy, the baby will be happy. At the time, I thought it was a nice superstition. But researchers are providing evidence that one's lifestyle choices may add to the blueprint of the next generation — a thought geneticists considered impossible.

Helen Thomson writes for New Scientist that past research showed “girls born to Dutch women who were pregnant during a long famine at the end of the Second World War had twice the usual risk of developing schizophrenia.”

Geneticists are puzzled when presented with cases such as these, as environmental factors aren't supposed to affect the genetic information contained within a sperm and egg. We are supposed to be born a “clean slate” as far as environmental influences go. But researchers have observed some human genes keeping some of these environmental markings, evading the cleanup process.

A group of researchers looked into the methylation patterns in fetal cells that later inform the fetus' own sperm or eggs. The chemical methylation has had a precedence in previous studies, where it proved to play a role in altering the gene expression in early childhood in humans and other animals. When too much stress is repeatedly put on an infant, the methylation process alters how well the child responds to stress later on in life.

Azim Surani and colleagues were surprised to find in their own studies that some of the fetal cells were not reset, as they would have expected.

Surani said to Thompson: 

"However, about 2 to 5 percent of methylation across the genome escaped this reprogramming."

The researchers noted that the affected genes were involved in certain metabolic functions that may lead to obesity, as well as certain neurological processes that could lead to schizophrenia and bipolar disorder. The good news is it seems there's a narrow window of time for these environmental conditions to be passed on. However, Surani is cautious about making any further conclusions until his team figures out why these genes manage to evade detection during the cleanup process.

Read more about the study at New Scientist.

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