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Transcript from video

We've always known the genes of our ancestors can be passed on through generations. But could they pass on something more than just their genes? Could a memory of my grandfather's lifestyle or my grandmother's diet somehow have been passed down to me? Not through their genes, but through something beyond their genes, something known as epigenetics.

Epigenetics literally means "above genetics." Epigenetics refers to the beacons that are added on top of the DNA.

It's all about what genes are on and what genes are off.

I think it's up there with the DNA code.

Epigenetic changes are like tags or beacons on our DNA. They can turn our genes on or off, just like a light switch. Now, the significance of this is huge.

These switches can actually control the way our genes behave. They can affect everything from emotional well-being, to how much we eat, and even the diseases we develop. Dr. Jeff Craig has been studying the causes and effects of epigenetic changes in children.

So, Jeff, what information can this slide give us?

Well, this shows a microarray of the whole human genome. And what it shows is spots of DNA which basically act like traffic lights. The green lights are where genes are on, and the red lights are where genes are off.

Most of us know a little about DNA, or our genetic blueprint. DNA consists of a long strand of four subunits known as A, G, C, and T. Our genes are basically a long string of letters, it's the way those letters are arranged that makes us unique individuals.

The DNA code is very important because the order of the letters tells you about the ordering of the amino acids that go to make the protein.

Proteins are the building blocks of life. They make every living cell in our body, from those of our vital organs to our hair, and even our fingernails. Identical twins, like Imogene and Tennille, have the same DNA, the same ordering of letters. But despite that, only one of these identical twins was struck down by leukemia, a devastating cancer usually caused by a genetic mutation.

Tenille.

That's not.

When was that taken? When was this photo taken?

At kinder.

Yeah? Why is this your favorite photo?

For five weeks before her fifth birthday, and like all kids, she was a bit off-color. She was pale, lethargic, and I thought she had a bug. I certainly didn't expect someone to come back and say she has leukemia.

With Imogene and Tennille, Imogene did not show a typical leukemia-associated gene-splicing event, as usually happens in a high proportion of leukemias. So that's why we think she may have had an epigenetic change.

In other words, Imogene's cancer wasn't caused by a genetic mutation, but by another mechanism that switched off an important gene that suppresses cancer. Fortunately for Tennille, the same gene remain switched on, and she showed no sign of the disease. We had hoped many of these phenomena about genes and their role in disease would be explained by mapping the human genome, but they weren't.

After the Human Genome Project, we looked at the number of genes that were found, 30,000. It's not really much more than a fruit fly. And we thought where is the complexity? What makes human bodies complex?

Experts now believe that complexity might be due to epigenetics, those tag or beacons that sit upon or DNA. But what causes them to appear? And can they be inherited by future generations? Recent research shows epigenetic tags can be caused by any number of environmental influences, such as smoking, pesticides, stress, and even diet.

Drs. Jennifer Cropley and Catherine Suter are at the forefront of epigenetic research into diet and obesity.

And here are the mice.

Wow. So why are they all different colors?

They're actually genetically identical. They're all twins, but they don't look the same. And it's due to the action of a particular gene, a single gene. All these mice have the gene. But in some of the mice the gene switched on, and in some of the mice, the gene switched off. And in this guy, it switched off.

Now, this little girl over here, identical in every other way only she's yellow, and that's because the gene switched on in this mouse. But unfortunately for her, the gene has another effect. And so this is what she's going to look like in about three months time.

Oh, she's large.

Isn't she huge?

Has she eaten too much?

She most certainly has. The same gene that causes the mice to turn this beautiful yellow color also causes them to overeat, and so they get obesity and Type 2 diabetes. It's an almost perfect model of Type 2 diabetes in people.

Incredibly, just one gene was controlling coat color and obesity. But what's even more incredible is that the mother's diet can determine whether the gene is switched on or off.

We found if we gave the dietary supplement, then she was more likely to have brown mice. That is, the diabetes gene had been switched off.

So will this mouse then pass on that epigenetic tag to her offspring?

Yes, she will.

So what you're saying is that a grandma's diet can actually affect two generations on.

That's right.

So if epigenetic changes can be inherited in mice, what about in humans? Catherine Suter and colleagues at Saint Vincent's Hospital found an epigenetic mark involved in cancer was passed on. It was an incredible breakthrough for medical research.

Now, we now know that there are a subset of people who don't have any spelling errors, any mutations in their DNA, but they still get these multiple cancers. And that's because they have an epimutation. A critical gene has simply become switched off when it should be on in every cell in their bodies.

So is it possible to reverse that process, to turn that gene back on? Well, the answer is yes. But the problem is, at the moment, the drugs are not selective. They are not capable of targeting just one gene.

We don't know what the rules are. What we do know is that genes are on or off, depending on certain proteins and chemical tags that are attached to the DNA.

Perhaps in the future, we will be able to wipe off those chemical tags inherited from our ancestors, and our own children may be able to selectively erase the epigenetic memories shaped by our lifestyles.