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Are you really what your mother ate, drank or got stressed about? The simple answer is 鈥渘o鈥�, but not in the way you think.

We are products of . Our genes and environments interact. And 鈥渆nvironment鈥� can be what we are experiencing now or at any time during our life.

An overwhelming body of evidence, from both humans and other animals, has shown that the environment we experience in the of life influences our risk of chronic diseases: conditions such as heart disease, diabetes, psychiatric disorders and some cancers.

Changes to 鈥� molecules that lie literally 鈥渙n top of genes鈥� 鈥� have been implicated as by which early environment (nurture) can leave a long-term change in the risk for chronic disease.

Nature, meet nurture

In a recent article in The Guardian, Adam Rutherford that the term 鈥渆pigenetics鈥� is now being abused by pseudoscientists in a similar way to 鈥渜uantum鈥� and 鈥渘ano鈥�. I鈥檇 like to argue that the term has not been misused any more than most scientific terms, bar the odd , or .

Although researchers sometimes disagree over the of the word 鈥渆pigenetics鈥�, it can be best understood through its conceptual development over time.

Aristotle didn鈥檛 like the prevalent idea in his day that we all grow from a microscopic version of ourselves. He coined the term 鈥渆pigenesis鈥� to describe the developmental process whereby a complex organism develops, through successive stages, from a simple start. This is essentially what we know today as developmental biology.

More than 70 years ago, modified the word to 鈥渆pigenetics鈥� and as 鈥渢he interactions of genes with their environment, which bring the phenotype [i.e. the set of observable characteristics of an individual] into being鈥�; my favourite definition.

Fast forward to 1996. A handful of notable scientists had already begun to theorise about the molecular nature of epigenetics. These ideas were summed up by Arthur Riggs and colleagues who epigenetics as 鈥渢he study of mitotically and/or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequence鈥�.

Epigenetic changes would involve small molecules jumping onto our genes. They would stay there, hanging on even through cell division (mitosis), providing a long term epigenetic legacy. 鈥淢eiosis鈥�, the cell division that results in eggs and sperm, implied that such changes could persist from one generation to the next.

Fast forward again to today. Most experts' definition of epigenetics centres around these small molecules. And what have we done with these small molecules? We now have replicated at least two of environment from the cradle to the grave: stress and smoking.

We have clinical biomarkers for cancer prediction, diagnosis and prognosis currently in clinical trials. And we have strong evidence that sometimes, events such as and in one generation can affect the health and epigenetics of the next. Such effects have also been shown in .

Epigenetic legacies

Is this all non-Darwinian? Certainly not; Darwin will not be turning in his grave because he that cells 鈥渢hrow off minute granules which are dispersed throughout the whole system鈥�. These 鈥溾�� would be 鈥渃ollected from all parts of the system to constitute the sexual elements, and their development in the next generation forms the new being鈥�.

Not entirely correct, but we do already have plausible (although not proven) set of epigenetic molecules that are for such particles.

Rutherford, in his Guardian article, rightly pointed out that epigenetic legacies may not last for more than a couple of generations. This may be because that epigenetic state has evolved to responds to environments that may change every few generations. In the longer term, it has even been that epigenetic change in response to environment may be 鈥渇ixed鈥� by a genetic mutation in the same gene that has a similar effect on its function.

I agree with Rutherford that much more work is needed. For example, the human studies of transgenerational effects on health that he showcases have not yet been linked to any specific epigenetic changes. Personally, I would draw the line at calling these effects 鈥渆pigenetic鈥� but wouldn鈥檛 go to war with someone who did.

Spot the snake oil

Epigenetics fascinates us all. Yes, we鈥檇 love to know whether diet, exercise and meditation really changed our genes. But to turn a handful of promising studies into a mountain of evidence or to fail to replicate such findings, will take time.

And we must never lose sight of genetics. After all, in around one fifth of genes studied, genetic sequence is a much stronger influence on epigenetic state than environment, and epigenetics and genetics are better able to explain disorders such as obesity.

And finally, can we begrudge the odd snake-oil salesman borrowing a technical term like 鈥渆pigenetics? , but a quick search of Google shows that reports of true scientific articles on epigenetics far outnumber those with a pseudoscience flavour. I credit the public with sufficient intelligence to sort most of the wheat from the chaff.

Let the (informed) debate begin.

is Principal Research Fellow at .

This article was originally published on .
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