you ever noticed that if you get to know two identical twins they might look alike but they're always subtly different yeah whatever as they get older those differences can get more pronounced two people start out the same but their appearance and their health can diverge for instance you have more gray hair no no I don't identical twins have the same DNA the exact same genes yeah and don't our genes make us who we are well they do yes but they're not the whole story some researchers have discovered a new bit of biology that can work with our genes or against them yeah you're heavier and I'm better looking yeah whatever imagine coming into the world with a person so like yourself that for a time you don't understand mirrors as a child when I looked in the mirror i' say that's my sister and my mother will say no that's your reflection and even if you resist this cookie cutter existence cultivate individual Styles and abilities like cutting your hair differently or running faster uncanny similarities Bond you together facial expressions body language the way you laugh or dress for an interview perhaps when you hadn't a clue what your sister was going to wear go the synchrony in your lives constantly confronts [Music] you when I see my sister I see myself if she looks good I think I look pretty today but she's not wearing makeup I say my God I look horrible it's hardly surprising because you both come from the same egg you have precisely the same jeans and you're literally clones better known as identical twins but now imagine this one day your twin your clone is diagnosed with cancer if you're the other twin what can you do except wait for the symptoms I have been told that I am a high risk for cancer HS over me and yet it's not uncommon for a twin like Anna Marie to get a dread disease while the other like clotilde doesn't but how can two people so alike be so unalike well these mice May hold a clue their DNA is as identical as Anam Marie and clotilde's despite the differences in their color and [Music] size the human who studies them is Duke University's Randy jle So Randy I see here you have skinny mice and fat mice what have you done in this lab well these animals are actually genetically identical the fat ones and the skinny ones that's correct cuz these are huge they're huge can we weigh them to find out so if you take this is looks like they can barely walk they they can't walk too much they're not going to be running very far so that's about 63 G 63 G let's look at the other one so it's half the weight right this gets even more mysterious when you realize that these identical mice both have a particular Gene called ay but in the yellow Mouse it stays on all the time causing obesity just look at this so what accounts for the thin Mouse exercise Atkins no a tiny chemical tag of carbon and hydrogen called a methyl group has a fixed to the AI Gene shutting it down creatures possess millions of tags like these some like methyl groups attach to genes directly inhibiting their function other types grab the proteins called histones around which genes coil and tighten or loosen them to control gene expression distinct methylation and histone patterns exist in every cell constituting a sort of second genome The epig genome epigenetics literally translates into just meaning above the genome so if you would think for example of the genome as being like a computer the hardware of the of of a computer The epig genome would be like the software that tells the computer when to work how to work and how much in fact it's the EP genome that tells our cells what sort of cells they should be skin Hair Heart you see all these cells have the same genes but their epigenomes silence the unneeded ones to make cells different from one another epigenetic instructions pass on as cells divide but they're not necessarily permanent researchers think they can change especially during critical periods like puberty or pregnancy jles mice reveal how the epigenome can be altered to produce thin Brown mice instead of fat yellow ones he feeds pregnant mothers a diet rich in methyl groups to form the tags that can turn genes [Music] off and I think you can see that we dramatically shifted the coat color and we get many many more Brown animals and that matters because your coat color is a tracer it's it's an indicator that's correct of the the fact that you have turned off that Gene that's right this epigenetic fix was also inherited by the next generation of mice regardless of what their mothers ate and when an environmental toxin was added to the diet instead of nutrients more yellow babies were born doomed to grow fat and sick like their mothers it seems to me this has profound implications for our health it does for human health if there are genes like this in humans basically what you eat can affect your future Generations so you're not only what you eat potentially what your mother ate and possibly even what your grandparents ate so how do you go to humans to do this experiment when you have these mice and they're genetically identical on purpose that's right who is your perfect Lab human well then we look for identical humans which are identical twins [Music] twins and that brings us to the reason why were showing you Spanish twins in 2005 they participated in a groundbreaking study in Madrid its aim to show just how identical epigenetically they are or aren't one of the question of twins is that if my twin has this disease I will have the same disease and genetics tell us that there is a high risk of developing the same disease but it's not really sure they're going to have it because our genes are just part of the story something has to regulate these genes and part of the explanation is epigenetics estellar wanted to see if the twins epigenomes might account for their differences to find out he and his team collected cells from 40 pairs of identical twins Age 3 to [Music] 74 then began the laborious process of dissolving the cells until all that was left were wispy strands of DNA the master molecule that contains our [Music] genes next researchers Amplified fragments of the DNA until the genes themselves became detectable those that had been turned off epigenetically appear as dark pink bands on the gel now notice what happens when the genes from a pair of twins are cut out and overlapped the results are far from subtle especially when you compare the epigenomes of two sets of twins that differ in [Music] age here on the left is the overla DNA of 6-year-old Javier and Carlos the yellow indicates where their gene expression is identical on the right is the DNA of 66-year-old anamarie and clotilde in contrast to the younger twins hardly any yellow shines through their epigenomes have changed dramatically the study suggests that as Twins age epigenetic differences accumulate especially when their Lifestyles differ one of the main findings of our research is that episomes can change in function of what we eat of what we smoke or what we drink and this is one of the key uh difference between epigenetics and genetics as the chemical tags that control our genes change cells can become abnormal triggering diseases like cancer take a disorder like MDS cancer of the blood and bone marrow it's not a diagnosis you'd ever want to hear when I went in then he started patting my hand and he was going your blood work does not look very good at all and that I had um MDS leukemia and uh that there was not a cure for it and basically I had 6 months uh to live Char coar was epigenetics the reason could the silencing of critical genes turn normal cells into cancerous ones it's scary to think that a few misplaced tags can kill you but it's also good news because we've traditionally viewed cancer as a disease stemming solely from broken genes and it's a lot harder to fix damaged genes than to rearrange epigenetic tags in fact we already have a few drugs that will work recently Sandra Shelby and Roy kwell participated in one of the first clinical trials using epigenetic therapy the idea of epigenetic therapy is to stay away from killing the cell rather what we are trying to do is diplomacy trying to change the instructions of the cancer cells reminding the cell hey you're a human cell you shouldn't be behaving this way and we try to do that by reactivating genes the results have been incredible and I didn't have really any horrible side effects I am in remission and going in the plus direction is a whole lot better than the minus Direction in fact half the patients in the trial are now in [Music] remission but while it may be easier to fix our epigenome than our genome messing it up is easier too we've got to get people thinking more about what they do they have a responsibility for their epig genome their genome they inherit but their epig genome they potentially can alter and particularly that of their children and that brings in responsibility but it also brings in hope you're not necessarily stuck with this you can alter this