Sins of the Fathers

Sins-of-the-fathers department: If great-grandpa was sprayed with a fungicide commonly used on fruits, a male rat is likely to have trouble finding female companionship. According to a study led by scientists at the University of Texas at Austin, exposure to the fungicide vinclozolin reverberates three generations later: female rats can tell the difference between male descendants of exposed and unexposed rats, the scientists are reporting this evening in the online Early Edition of the Proceedings of the National Academy of Sciences.

This might seem like just a quirky finding except for one thing: it comes in the midst of a revolution in biologists' understanding of what are called trans-generational effects. The term refers to consequences of toxic exposure that strike a generation or more down the line. In the case of vinclozolin, the chemical affects how genes in the male rats' sperm are turned on or off. (This is called an epigenetic change.) All the male rats that inherit the damaged DNA get sick young, and the damage persists down at least three generations, to the great-grandsons of exposed rats.

That kind of transgenerational genetic change was first reported in 2005 by scientists led by Michael Skinner of Washington State University; until then, no one knew that the effects of environmental toxins can be felt down through the generations. It doesn't happen through harmful mutations, which become rarer with each generation. Instead, the culprit seems to be molecular "on" and "off" switches that get attached to the sperm's DNA, and which do persist through the generations. Today's study is the first to show that females can tell something is wrong.
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