In general, when a certain disease or condition “runs in the family”, there is a genetic link that explains why. Knowing what genes raise the risk of developing certain diseases enables people who have those genes (or gene mutations) to seek a treatment plan. A study looks at things quite differently. The “toxins” that affected your great-grandparents could affect you – even if you didn’t inherit a gene mutation.
A study was done on rats in the laboratories at Washington State University in 2005. It was the lab of Michael Skinner. A research fellow informed him that she had accidentally taken an experiment one step too far, by breeding the rats in the study to the fourth generation.
In this study, the researchers exposed pregnant rats to an endocrine disruptor for the purpose of gaining more insight into the process by which an unborn fetus becomes either male or female. They used a agricultural fungicide called vinclozolin. It didn’t appear to affect sexual differentiation in the rats at all.
Since they had bred the fourth generation of rats, the decision was made to go ahead and analyze them. What they found was unexpected. The rats that were three generation after the pregnant mother rats who were exposed to vinclozolin had abnormally low sperm counts. It wasn’t due to a change (or mutation) it their DNA sequence.
They repeated the study, and looked at rats who were the fourth or fifth generation from the pregnant mother rats who had been exposed to vincolzolin and found the same results. Michael Skinner explained the results of the studies as “what your great-grandmother was exposed to could cause disease in you and your grandchildren”.
These results were so unexpected that they gave rise to a new field called transgenerational epigenetics. It is the study of inherited changes that cannot be explained by traditional genetics.
How does this relate to genealogy? It could mean that the medical family trees that people collect might not be quite as informative as they were previously thought to be. It suggests that in addition to noting which relatives had a certain disease, and checking to see if you have the genes related to the disease in your DNA, we need to do more. Maybe we need to ask what chemicals great-grandmother had been exposed to.
Others have pointed out some potential issues with the studies. Some feel the rats were exposed to an amount of vincolzolin that was much higher than a typical human would be exposed to. There is a suggestion that this means one cannot extrapolate the results of the study to be how things work in humans. More studies, that replicate Skinner’s, need to be done.
Image by Jean-Etienne Minh-Duy Poirrier on Flickr.
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