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epigenetics explained

April 7, 2009

Growing evidence indicates there is more to heredity than DNA, that heritable non-DNA variations can take place during development, sometimes in response to an organism’s environment. The notion of soft inheritance is returning to reputable scientific inquiry. Moreover, there seem to be cellular mechanisms activated during periods of extreme stress that trigger bursts of genetic and non-genetic heritable variations, inducing rapid evolutionary change. These realizations promise to profoundly alter our view of evolutionary dynamics.

Collectively, the processes that we believe have been neglected in evolutionary studies are known as epigenetic mechanisms. Epigenetics is a term that includes all the processes underlying developmental flexibility and stability, and epigenetic inheritance is part of this. Epigenetic inheritance is the transmission of developmental variations that have nothing to do with changes in DNA base sequences. In its broad sense, it covers the transmission of any differences that do not depend on gene differences, so it encompasses the cultural inheritance of different religious beliefs in humans and song dialects in birds. It even includes the developmental legacies that a young mammal may receive from its mother through her placenta or milk — transmitted antibodies, for example, or chemical traces that tell the youngsters what the mother has been eating and, therefore, what they should eat. But epigenetic inheritance is commonly associated with cellular heredity, in which differences that arise among genetically identical cells are transmitted to daughter cells.

…we now know that cellular epigenetic variations are transmitted not only within organisms, but sometimes also between generations of organisms, via their sperm and eggs.

The mechanism about which we know the most is DNA methylation.

One interesting and important discovery is that stresses — unusual conditions difficult for organisms to cope with, such as extreme heat, starvation, toxic chemicals, or drastic hormonal changes — are potent inducers of heritable epigenetic change.

in Incubator / by Eva Jablonka / January 6, 2009
via Extending Darwinism § SEEDMAGAZINE.COM.


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