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qeg001

http://boards.history.com/thread.jspa?threadID=700021129&tstart=30&mod=1192626787430

Epigenomes and a new branch of science

Oct 17, 2007 6:13 AM
This is exciting stuff. We all know that the genes that make up our DNA control many aspects of our lives, like the color of our hair, but what controls our genes? The answer is epigenes. 

The cells of your teeth, eyeballs, skin, and liver all have identical DNA, but different epigenes. The epigenes turn on and off certain genes to get the cell to develop correctly. Genes are the hardware; epigenes the software. Or if you like, genes are the factories, and epigenes are the little guys who decide what the factory will produce. 

Now here's the exciting part - over the course of an animal's life, his or her epigenes change to meet the situation. If that being is creating eggs or sperm (a girl in the womb or a boy in early puberty), the imprint of those epigenes are recorded for the following generation. 

To my mind, this is a mechanism for guided evolution. We've all heard of the bizarre experiment where animals trained in mazes have offspring that know the maze (inherited learning), and we've all experienced dogs with built-in instincts (like herders who love to herd anything, even if raised in the city). Perhaps the abilities learned in one generation create epigenomes that are then passed on to subsequent generations. 

Similarly, perhaps cormorant birds in the galapagus learned in their lifetime that their flying abilities did them no good. Flying was a waste of nutrients. This information was then passed down via epigenes to their offspring. As a result, cormorants in Palau are the only such birds without the ability to fly. 

The evidence of epigenes affecting us throughout our lives comes from animal and human experiments. Identical twins at an early age have nearly identical epigenes (this can be directly measured by chemical markers). Later in life, their epigenes have drifted apart (again, measurable). Thus while identical twins may have the same appendicitus at age 3, only one of them gets cancer at age 60. The evidence of transgenerational effects are also based on animal and human experience. Animals fed certain diets or raised with greater attention pass on traits not just to the next generation, but for all generations thereafter. Similarly, the grandchildren of human famine survivors have measurably different odds of diabetes (oddly enough, famine improves our resistance - diabetes is rising mysteriously in the US, the cause may be too much food in our grandparent's diet). 

More can be found at http://www.pbs.org/wgbh/nova/ from the episode entitled "Ghost in our Genes."
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