Over the last decade, our knowledge of the human genome has exploded, but it often seems like the more we learn, the deeper the mystery grows. We have a basic understanding of what many of our 23,000 genes do, but that understanding has not translated into a particularly great ability to predict who among us will develop common pathologies like diabetes or coronary artery disease.
But the cutting-edge field of epigenetics is trying to change that. Geneticists working in this area are looking for heritability mechanisms that go beyond our genes, and researchers at UCLA recently made an important discovery in that direction.
John Torday and Virender Rehan wanted to know if smoking can have negative health impacts multiple generations into the future. To test this, they injected female rats with nicotine and then analyzed the lung function of their progeny. What they found was stunning: Two generations down the line, the grandchildren of the nicotine-injected rats were more likely to have asthmatic lungs than control subjects. And, this occurred in the absence of any genetic mutation across the generations.
So, how is it that a disease like asthma could become heritable without a genetic change? To answer that, the researchers (and their geneticist peers) are increasingly looking to the 98 percent of the human genome that is not directly involved with protein coding (as opposed to the 2 percent of the genome that is made up of those 23,000 genes). This vast territory used to be referred to as "junk DNA" for its apparent purposelessness, but it's increasingly clear the pejorative was misapplied: This junk DNA seems to be critically involved with gene expression, and it's here that epigenetic influences like smoking probably make their mark.
One of the first things kids used to learn in high school biology is the folly of Lamarckian evolution- the idea that environmental and behavioral forces can shape heredity (ie: that giraffes developed long necks because successive generations kept stretching after higher leaves). Studies like this one from UCLA, however, suggest that Lamarckian thinking may not be totally wrong after all. While no one is claiming that you can pass on your abs of steel to your grandchildren, it does seem increasingly certain that heredity is much more complicated than we thought.
H/T Eureka Alert
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