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Health and Medicine




Exploradio - The other side of evolution
Darwin's theory says mutations drive evolution.  The new science of epigenetics describes other mechanisms for change that don't involve DNA.
by WKSU's JEFF ST. CLAIR
This story is part of a special series.


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Jeff St. Clair
 
Biochemist Nikki Harter specializes in how newly discovered micro-RNA plays a role in melanoma. Micro-RNA is an epigenetic factor that controls life inside the cell independent of the DNA.
Courtesy of J.St.Clair
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Darwin expounded on natural selection as the basis of evolution back in the 1850’s.  One hundred years later, Watson and Crick introduced the DNA molecule, and a mechanism for evolutionary change.

Another 50 years, and the Human Genome Project sequenced human DNA with its 25,000 genes.

Now a new chapter is opeing in our understanding of how we get to be who we are. It’s called epigenetics. In this week’s Exploradio, we look at how epigenetics is providing insight into cancer research in Cleveland.

Exploradio - The other side of evolution

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Dutch famine study

It was in the dark days of World War II that Europeans suffered incredible hardships. Malnutrition was common in Britain and across the continent.

And  the lasting effects of those stresses have led to a new branch of science called epigenetics.

Epi  or “above” genetics looks at mechanisms other than genes that determine inherited traits.  The head of Case Western Reserve University’s biology department, Chris Cullis, offers the example, the lasting effects of famine in a Dutch village during World War II.

“The starvation of the population in the second World War… where they’re now finding there’s an association of the women who were suffering that and the body mass of their grandchildren. If you’re looking for epigenetics, you have to look not at the next generation but the generation after that because that’s where the effects are observed.”   

Cullis says pregnant women who were malnourished during the war passed on this stress to future generations.

It’s a startling departure from our usual understanding of how genes alone determine characteristics. It was once thought that changes only happened through mutations of genes. That’s the basis of Darwin’s theory.

Heredity beyond genes 

Now Cullis says, epigenetics is showing that even if the DNA is unchanged, factors that affect animals during their lifetime, such as stress, can be passed on.

“If you have children who are poorly nourished, what happens to their children or their grandchildren? Are their DNAs actually different from those who have been well nourished, for example?  Or is really all epigenetic, that is, there is a change in the expression, but we don’t change the sequence.” 

It turns out that genes are much more complicated than originally thought.   It’s not just our DNA that makes us who we are; it’s also what controls the genes.

Mutation vs epigenetics 

Case biochemist Nikki Harter explains it this way.  She says imagine DNA is a street, a mutation is like a pothole. It’s damage to the street that stops your car. But …

“Epigenetics is different in the sense that if you had a tree falling onto the street, it’s not affecting the street in the sense of damaging the street. But it still will not allow that car to go further.”

Either way the car, or the gene’s function, comes to a standstill. 

Harter says the tree in the road, the epigenetic factor, can have many forms.  It may be that chemicals turn off or turn on certain genes, or blank out whole stretches of DNA.  The epigenetic trait she’s studying is a newly discovered type of RNA called micro-RNA. 

Micro-RNA and melanoma 

“Micro RNAs, because they’re interfering with the flow of information, this is the basis of epigenetics. And in fact, these micro RNA’s have been now tightly linked to a number of forms of cancer.”

Harter has found that in some people sunlight generates micro RNAs that she thinks could be a cause of melanoma.   She speculates that, like the traits seen in the World War II famine study, melanoma could be a family trait not because of genes, but because of what’s acting on the genes.

“Sunlight, natural sunlight, can be very impactful in the sense of creating an epigenetic change which ultimately could be passed on to your progeny or offspring.”

Harter is studying the effects of sunlight on the skin and how epigenetics may help us understand melanoma.   The National Institutes of Health is also exploring the new science of epigenetics.  It hopes in the next few years to complete an epigenetic roadmap similar to the human genome project.

 


Related Links & Resources
NIH Epigenetic roadmap project

Epigenetics wiki

Dutch famine WWII

Listener Comments:

My Favorite!!! Nicely explained!


Posted by: D (Biology) on January 11, 2012 10:01AM
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