Essay about Epigenetics

1361 Words Feb 21st, 2013 6 Pages
ONE of biology’s hottest topics is epigenetics. The term itself covers a multitude of sins. Strictly speaking, it refers to the regulation of gene expression by the chemical modification of DNA, or of the histone proteins in which DNA is usually wrapped. This modification is either the addition of methyl groups (a carbon atom and three hydrogens) to the DNA or of acetyl groups (two carbons, three hydrogens and an oxygen) to the histones. Methylation switches genes off. Acetylation switches them on. Since, in a multicellular organism, different cells need different genes to be active, such regulation is vital.

What has got a lot of people excited, though, is the idea that epigenetic switches might be transmitted down the generations.
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It was done in rats, but a rat’s physiology is sufficiently similar to a human’s to suspect the same thing may be true in Homo sapiens. In a nutshell, Dr Rehan showed that if pregnant rats are exposed to nicotine, not only will their offspring develop the asthma induced by this drug, so will the offspring of those offspring.
Dr Rehan and his team injected their rats with nicotine when they were six days pregnant. (Rat pregnancies last 22 days.) They then allowed them to give birth and raised the pups to the age of three weeks, before some were examined. The rest were allowed to mature and breed, and their own offspring were similarly examined. There was, however, no further administration of nicotine.
The pups of the treated mothers had asthmatic lungs. The organs’ airways were constricted, and molecular analysis showed abnormally high levels of fibronectin and collagen—which would stiffen the lung tissue—and also high levels of receptor molecules for nicotine. That was expected, since the developing embryos were exposed to the nicotine when their mothers were treated. However, when the team did similar tests on the grand-offspring of the treated mothers, they got similar results. Those grand-offspring had not been exposed to

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