The Secret Life Of Twins (2009) s01e02 Episode Script
Part 2 of 2
It's hard not to do a double take when you see identical twins.
As nature's clones, they're without doubt fascinating to us and to each other.
The minute we saw the twins, we were looking at them and comparing.
I think it's amazing seeing loads of twins because I think other twins are weird.
But they're not just intriguing to look at.
These genetically identical individuals are invaluable to scientists who are desperate to unravel the nature/nurture debate - are we born or are we made? We always think of them as slight oddities of nature, but they can help you and I to uncover really important diseases that are affecting us all.
Last time we met identical twins who were remarkably similar, not just in the way they look but in their personalities and their approach to life.
I've tried to commit suicide quite a few times.
I was actually going to die if I kept going the way I was going.
Despite leading very different lives on opposite sides of the world, Ian and Paul suffered almost identical heart conditions.
After all this time of doing the right thing, I find out that I'm no different from my brother.
Even twins like Mia and Alexandra, who were growing up on separate continents, have loads in common.
That look right there, that was Mia.
Twin doctors, Chris and Xand Van Tulleken discovered that their genes make them identical in some surprising ways, from how they vote, to their maths ability and whether or not they'll take risks.
I'm a bit worried about him.
Are you worrying about me? I don't care at all about you.
I'm worried about my feet getting cut.
But having identical DNA doesn't make twins exactly the same, as Chris and Xand discovered in a test for pain tolerance.
I was wincing at the beginning but now I'm dying.
It's these intriguing differences between identical twins that we're exploring in tonight's programme.
Do you and I behave differently? The answer is yes, we do.
I think the answer to that is no we don't.
We'll find out how dissimilar Chris and Xand actually are and we'll meet other identical twins who are incredibly different.
So even though she was born five minutes ahead of me, I'm ten years older than her? Including fat and thin twins, Noora and Miia in Finland.
Oh, my god, I'm going to be as heavy as she is and I have to wake up now.
And Mark and John in America who have one striking difference.
No-one has ever asked me if I'm gay because my brother is.
We'll discover that although our genetic make-up is fixed at conception, the environment can start to shape us even before we're born.
And we'll explore one of the most exciting new areas of science, revealing how our lifestyle can affect the actual workings of our genes.
SIRENS SOUND All children are fun, but twins are twice as entertaining and double the trouble.
People often say to me, "so who's the good twin and who's the evil one?" I'll say Tal and she'll say Cel.
Each year in the UK, identical twins are born to around 4,000 couples.
Would you like to hear the babies? In just a few months, Hermie and Colin Willets will join them and their son Thomas will have two new identical baby brothers to play with.
It was very exciting when Hermie told me she was pregnant, I mean we were just bracing ourselves for one and then we found out that it was two, didn't we? We went for quite an early scan so it was around eight weeks.
Yeah, well, have a listen then, tell daddy what does it sound like? Boom, boom.
We were just more concerned about them finding a heartbeat and she said, "Here's a heartbeat" and showed me.
Then she looked again and said, "Yeah, that's it, there's two.
" I don't think Colin spoke then for the rest of the session.
No, it's one of the only times in life, and people say that they were speechless, but I genuinely was speechless for about 20 minutes, I really didn't know.
You were almost in hysterics, weren't you? I genuinely was speechless for 20 minutes.
We'll be following Hermie's very special pregnancy throughout this programme.
It started out in exactly the same way as her first pregnancy.
A single egg was fertilized by a single sperm.
But this time, the embryo inexplicably divided at some point in the first week to form two identical twins, something that's always been considered a scientific phenomenon.
The two new babies have identical DNA, but throughout their lives, differences will emerge, and this is like gold dust to scientists.
For years, scientists have been trying to work out how much we're all shaped by nature, our genes, as opposed to nurture, our environment.
Studying twins who share the same genes is one of scientists' unique ways of exploring this question.
In the next stage of their journey, identical doctors Chris and Xand want to see whether their own differences can help them to find answers.
Do you have freedom in your life to make decisions to change the way you are and the way you live? Xand wants to prove that their different experiences have shaped them more than their identical genes.
We deal with people in a subtly different way.
You're quite confrontational, quite straightforward with people.
I tend to be more conciliatory and relaxed.
It's a different thing.
If I So you're saying that we behave Look at how confrontational you're being.
To prove his point, Xand is taking his brother back to St Thomas's for a full examination to reveal all their physiological differences.
They're being tested for bone density, pain tolerance Ow! .
.
and lung capacity Right, keep going.
.
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as well as height, weight and grip strength.
Keep squeezing harder, harder, harder, harder, harder, harder, harder, stop.
OK.
Well done.
Yours was 65 kilos.
Really? Yeah, and yours was 39 kilos.
What? Give me that one, give me that one - there's got to be some problem with the machine.
OK, we'll do best of five.
The Department of Twin Research has run these tests for nearly 20 years on thousands of twins.
Professor Tim Spector has met many of them.
Today he's got some interesting results for Chris and Xand.
The key statistic here is the percentage fat difference between you.
Xand has 30 and you have 19.
Oh, that's terrible, isn't it? Which is a huge difference.
Yeah, that's terrible, isn't it? So he's actually at a very good level and you are unfortunately A disgrace.
The wrong side.
A disgrace to your genes.
That is bad, isn't it? A disgrace to MY genes is more to the point.
With 11% more body fat, Xand weighs in 15 kilos heavier than Chris.
That's very unusual.
Most identical twins are incredibly similar in weight, rarely more than three or four kilograms apart.
In fact, studying twins has shown that just like height and eye colour, our weight is definitely influenced by our genes.
But genes are not the whole story.
Puzzled by their weight difference, Chris and Xand want to know whether different lifestyles could be the cause, so they're going to do a study of their own.
So are you still fat? I'm not any slimmer than I was the last time that I saw you.
Right, so still fat then? Pretty much.
How's that working out for you at Harvard? It's all right, I don't have to move much so it's quite nice.
I'll bet it is.
It would be quite interesting to know how much exercise and how much moving around we're doing in a week compared to one another, and also to keep some sort of food diary to see if you really are eating less than me.
Step measurement's quite a good way of just assessing the differences in activity in our day.
It won't give us an absolute calorific value, but it's a good comparator, isn't it? For the past year, Xand has been living in Harvard, where he's being doing a degree and writing a book.
As a result, he spends a lot of time sitting in libraries and at his desk.
In contrast, Chris cycles almost everywhere.
His daily commute to and from the hospital where he works is five miles, and once he gets there, he's on his feet all day seeing patients.
Some days he barely has time for lunch.
But are these lifestyle differences really big enough to outweigh the influence of their identical genes? From the pedometers, every month you're doing the equivalent of walking from London to Bristol, is that right? Yes, and cycling from London to Manchester.
And doing the cycling as well.
And what were you doing? Well, I'm not really getting outside the M25.
I'm getting from London What are you doing in a day? I'm getting from the middle of London to the outer edges of London.
My shoes don't fit, I've got chafing on my inner thighs from all the fat.
Yeah.
So you're eating, we reckon, about 12 more hamburgers a month than me, the calorific equivalent of about 12 hamburgers more, 12 large hamburgers.
It doesn't seem that much, but think of the 12 hamburgers piled on the plate.
Piled around your waist.
That's the problem.
The 12 hamburgers go right there, don't they? Certainly in my case, my weight gain is environmental, not genetic.
But twin studies are revealing that Xand can't blame his lifestyle alone for his weight gain.
It's estimated that a billion people worldwide are overweight - that's one-sixth of the earth's population.
In fact, the World Health Organisation claims that obesity is fast becoming as big a problem as malnutrition.
So it's crucial for scientists to understand exactly what causes us to put on weight.
Once again, identical twins are providing some answers to this very common problem.
And that's, may I say it aloud? Yeah.
77.
2 kilograms.
OK.
Noora and Miia Simola are only 24, but already Noora weighs 17 kilograms more than Miia.
They're taking part in research by the University of Helsinki to understand what causes us to put on weight.
Where are we Noora right now? We are at strenuous.
Twins like Miia and Noora provide detailed information about their activity levels throughout their lives.
One of our important findings is that teenage years are very important in terms of what habits you then follow later on in your life.
So if you become physically inactive, that tends to persist and tends to be so in the adult life as well.
This is what happened to Noora.
When she went to college, she stopped eating healthily and exercised less.
I was studying till late night and didn't have the strength to do anything afterwards.
I just started walking and jogging alone in the same places.
Yes, because you have the time in the evenings and you were alone and doing anything.
But I have been with my boyfriend seven years, that's also one thing when you kind of settle down, you don't even have to care about your looks that much any more because you have this one guy.
You're not picking up some guy.
Yeah.
Noora is living proof of a new discovery helped by the study of twins.
Scientists now know that putting on weight actually changes the way our fat cells work.
We see very clearly that the obese co-twin's fat tissue is less efficient, it's not using energy very well.
Whenever the people eat, it just stores the fat in the fat tissue and this, of course, then means that weight loss might be more difficult and putting on weight would be very easy.
The discovery explains why putting on weight is easier than losing it.
And it's helping to show why some people stay the same weight no matter what they eat.
The key is to understand how our lifestyle interacts with our genes.
It seems that twins who differ widely in weight share food sensitivity genes which trigger rapid fat buildup when either of them eat excess food.
Twin studies are helping scientists identify these genes.
We have found evidence that one of the genes involved in appetite control called ghrelin is in fact differently distributed in the discordant pairs where one is obese, one is lean.
Professor Kaprio's conclusion is that our appetite is determined by our genes.
Genes that increase our appetite and cause us to put on weight easily were probably an advantage in times of famine.
The problem for people like Noora is they're never short of food.
As Noora's twin, Miia shares the same genes, so she will really have to watch her diet if she wants to stay slim.
I think it's a good thing that she is heavier than me, because when, when I was 63 kilos and I saw that she was a bit heavier than I, I was like, "Oh my god, "I'm going to be as heavy as she is and I have to wake up now and I have "to get the weight down because it's so much harder for her.
" So it was good the wake-up call for me that I could see the same body as mine and compare it to mine.
Twin studies have shown that different lifestyles can affect the way our genes shape our bodies.
It's not just how we put on weight but also how we age.
The hands of time touch everyone, but these two identical twins are concerned they may not be ageing at the same rate.
Sue and Shelagh Wright don't look the same any more.
But as children, they were so similar, even they can't tell who was who.
That one is me because that one I think looks more intelligent.
Although this one is looking rather cute and studying the plant.
Maybe that, I don't know.
Both Shelagh and Sue married their Mr Rights.
But sadly Sue didn't live happily ever after.
Her husband was diagnosed with a very serious illness.
With Huntingdon's Disease, my husband actually had the severe psychiatric symptoms.
He became violent and would assault me, so I had to leave the marital home for my own safety.
Sue got involved with an online support group for Huntingdon's, but this wasn't always a good thing.
Because it's such a grim disease, people choose suicide, so I would often be trying to talk people out of suicide.
So being a smoker, I would sit there at my desk puffing away far more than probably would have been the norm in other circumstances.
It's pretty stressful.
It can have its rewards too.
I've always said, for whatever reason, life's been very kind to me and not nearly as kind to my twin.
Shelagh has always been sympathetic to Sue's plight, but can't relate to some of her lifestyle choices.
I don't know why Sue started smoking, but I had one cigarette and turned green at the gills and decided it wasn't for me.
I decided not to abuse myself in that way.
And then because I have been at work for much longer, I've been able to keep more physically active.
To find out whether these different life experiences have affected how old they look, Sue and Shelagh are visiting the L'Oreal Laboratories in Paris.
The scientists here make a very detailed analysis of Sue and Shelagh's skin measuring differences in hydration, elasticity and wrinkle depth to determine how they're both ageing.
I'm just hoping my wrinkles won't look like Mount Everest and the Grand Canyon.
By analysing the skin of 1,000 twin pairs, the researchers hope to work out exactly which lifestyle factors make us all age.
We can make a sort of a weighting of different factors like the sun, like tobacco, like food, like stress, from professional stress to family stress or sickness.
All these thing can induce some rapid ageing.
They hope to prove that your life is quite literally written in your face.
Having gone through the whole range of tests, it's time for Sue and Shelagh to find out who has the older-looking skin.
The first thing I have to say is you have a very young skin in term of mechanical properties, you have very young skin.
Now, in term of clinical aspect, the ageing process When we look at a replica, we can see a light increasing depth of your wrinkle, Shelagh, in comparison with Susan.
And when we calculate your apparent age with the different clinical scores, we can see that you look four years younger than your sister.
Oh, you didn't anticipate that.
I'm delighted that I seem to have come out better on this when I anticipated coming out worse.
But perhaps it could be a problem of a body mass index of weight.
The fact that Sue is carrying extra weight seems to outweigh the effects of smoking and stress, making her skin at least appear younger.
At a certain age, many women feel the need to choose between their body and their face, because losing weight can make you look older.
Don't really want to end up looking like a bloodhound.
Sue's surprising result shows how complex the relationship between the environment and genes is.
But the signs of ageing are more than skin deep.
They're found in every cell in our body.
Our cells continually divide and with each separation, the chromosomes are duplicated.
But each time this happens, part of the chromosome tip, called the telomere, gets shorter.
So the length of our telomeres shows us how fast our cells are ageing.
So, are Shelagh and Sue's biological clocks ticking at the same rate? They're hoping Professor Spector at the Department of Twin Research will have some answers.
Compared to the average woman, both of you are actually doing pretty well telomere-wise, but there is a ten-year biological difference between you.
You've got the longer telomeres, you've got the shorter ones.
So even though she was born five minutes ahead of me, I'm ten years older than her in my body.
So, that's right, you know, these are only very rough approximations and we found in our studies using thousands of people, it shows average most of the differences between a smoker and a non-smoker, or someone who's fat and someone who's thin is around eight years' difference, and similarly someone in a high social class, low social class, between eight and ten years' biological difference.
So it makes sense that once you add up these differences between you two you get a similar sort of result, of this, this difference between you that actually, you know, you're doing particularly well even much higher than the average, and you are ten years behind, if you like.
Though Sue's skin appears younger, her experiences in life have aged her body cells faster than Shelagh's, despite sharing identical genes.
Cellular ageing leads to more than just wrinkles - it increases the risk of illnesses like osteoporosis, arthritis and cancer.
It shows that in combination with the genes you're born with, your environment at every stage of life can have a major impact on how well your body will work.
With this in mind, Xand wants to find out if events in his childhood could have left him more prone to weight gain than Chris.
You kept getting these punctured eardrums and that started at quite a young age, and that did not happen to Christopher, and eventually they put grommets in the ear which was supposed to clear it.
They're supposed to drop out after a year and yours didn't.
So we had to have them taken out.
And then you couldn't swim.
Christopher, in the meantime, was swimming so that made a difference at a young age, and then as a result of that, you had to have your tonsils out or your adenoids orI don't know.
When I had my tonsils out, I was told I could eat whatever I wanted afterwards and I was really looking forward to that, and I was told ice cream would be nice, and I didn't want ice cream, I wanted pork pies.
I remember this really clearly.
I was told I could have as many pork pies as I want, and I must have eaten 2o pork pies a day or something.
The little ones, the little ones.
And I'd completely forgotten this until you said it and I remember I think you sort of said, "Well, it's not quite what most people have for tonsillitis.
" That's right, so even then we had the circumstances of Chris busily swimming and probably eating carrots and Xand in hospital No, you were.
.
.
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with his television and eating pork pies.
Perhaps their different exercise levels and attitudes to food as children hold the key.
Did they establish a lasting pattern that's causing Xand to gain weight more easily than Chris? The idea that small chance experiences in childhood can have a lasting effect on our lives is one that intrigues scientists like Doctor Kathryn Asbury.
With identical twins it's easiest to think of it as parallel universes, you've got this same set of DNA going out into the world and bumping into slightly different people, slightly different experiences.
Someone might fall down in the playground and break their leg and be off school for six weeks and that might make a difference to the friendships they make and how they perform in school.
And it's these tiny experiences, these tiny parts of life that add up to make us who we are, I think, along, alongside our genes.
Some of these chance events can have a positive impact on our lives, but others can have a much bigger, more devastating effect.
Saturday you've got ballet, then the party.
Olivia and Isabella Murphy look and act like any other six-year-old girls.
For their early years, Olivia was almost indistinguishable from her identical twin sister.
But then she went through a terrible ordeal.
We're both the same size but I was poorly, and I the medicine made me go small.
Around about the age of two and a half, I noticed Olivia hadn't been feeling well for quite a while, and decided that I would take her to the GP for a blood test.
She was looking very pale and anaemic, really sleepy.
They then came back and said, oh, unfortunately the reason why Olivia is so anaemic is that she has the childhood cancer leukaemia, and yeah, that was in July, and straight away we were sent up to Great Ormond Street.
To tackle the leukaemia, Olivia was put on an intensive course of chemotherapy.
On the chemotherapy, Olivia lost her hair so straight away, they lost to me their little twinness.
A lot of the time if I had both girls they would say, ooh, you have one of each, a boy and a girl, and sometimes I would say, "No, actually, this is a girl," and sometimes I would just let it ride.
She had no hair but it's not funny.
Cos a girl having no hair, it's because she was poorly and As Isabella was getting taller, healthier and Isabella Olivia lost loads of weight and for quite a long time she also couldn't walk and she was getting smaller and frailer.
And she thought I was dead.
I thought, yeah, but I found she was gonna, she was nearly gonna die.
Olivia underwent two years of treatment for leukaemia, which took its toll on her and her twin.
It was very hard for Isabella, definitely, because she'd been used to having her sister to play with and all of a sudden she didn't have that any more, and she didn't have me around as much any more, and every now and then I do catch them talking about it.
Isabella would say, "You've got to spend lots of time with Mummy "in hospital", and Olivia would say, "Well, you got taken to Legoland.
" So, yes, for everyone involved it was, it was quite a tough time.
Breathe in deep.
The fact that Olivia developed leukaemia was obviously a tragedy for the family, but as her twin sister Isabella remained healthy, it was a great opportunity for scientists to explore why.
It has long been suspected that there's a genetic basis to leukaemia but exactly how it started in Olivia was a mystery.
Quite often in twin pairs that we've studied for many years, both the twins will have leukaemia pretty much the same time, they share the same disease.
So that begs the question what's going on in this twin pair, Olivia and Isabella.
Now, we think it's probably in a way just bad luck but something probably triggers the disease and all the evidence we have suggests it's probably infection, so we suspect Olivia had an infection.
We know she had tonsillitis of some kind, and it was probably that that triggered the leukaemia and her sister escaped because she didn't have that particular infection.
But tonsillitis doesn't cause leukaemia by itself.
With funding from Leukaemia Research, Professor Mel Greaves compared the girls' genes, searching for mutations triggered by Olivia's infection to cause leukaemia.
We first of all characterised Olivia's blood and the types of mutations she has in her blood cells, then we went to Isabella's blood, and what we were able to find are low levels of leukaemic cells having a single mutation, in contrast to her sister Olivia, whose leukaemic cells have five mutations.
Born with that first mutation, Isabella will always face the risk of developing leukaemia just like her twin.
But, fortunately, both she and Olivia have blood tests every six months to keep an eye on this.
Obviously, I briefed them on the fact that they will have to give blood and I don't think they're too pleased, but, after a little bit of encouragement, they're OK.
Thanks to Olivia and Isabella, scientists are now able to identify pre-leukaemic cells before the disease has started.
It gave us unique access for the first time to the early stages in the evolution of the disease, where, in essence, Isabella has the fossil evidence of how this disease evolves and develops, so it was a unique opportunity to look at the earliest stages of the disease that we couldn't otherwise have had.
And what's more, scientists are discovering that these very early stages of leukaemia even start before birth.
Identical twins, including, the girls, Isabella and Olivia, share a single placenta in mum's womb when they're developing as babies, and the consequence of that is they actually share each other's blood, so leukaemia might start before birth with a mutation of the DNA.
So leukaemia isn't simply inherited in your genes, it's a complex disease caused by a combination of chance environmental effects and our DNA.
Twin studies continue to reveal how the environment affects us as adults, as children, and even before we are born.
Images like these, produced with cutting-edge ultrasound technology are giving researchers an unprecedented view of babies' lives inside the womb, and they're helping to reveal how conditions in the womb can shape our development much later in life.
Today is an important chance for Colin and Hermie Willits to see how their unborn twins are developing.
Hermie very nice to meet you, and Colin.
Hi.
Right.
Do come along to the scanning room.
Professor Campbell is a pioneer of 4D ultrasound and over the years has seen thousands of pregnancies.
We have to put a layer of gel so that all the air pockets in the skin, but I hope it's not cold.
Is it not cold? Just a little.
So one head down, the body at the, on the left, one head up and the body on the back is on the right.
OK.
OK, so this is twin one.
And there's the little face, that's the baby that's, looking down.
What a good-looking baby.
Yeah, and it's amazing to see their expressions.
Yeah.
It's just quite nice to be able to, to see them as they are and to say hello, really.
I think it's making it, a little bit more real, I suppose.
I think I'm still in denial.
So this is twin two, and there, and this is the heel of the other one.
So these are the legs of twin one.
This is the hand of twin two.
So twin two may be going to hold the leg of twin one at any, any second I think.
The twins are so close together it looks as if twin two could reach out and hold the leg of twin one.
Contact between twins might not be intentional, but this closeness could be the start of that special bond that so many twins appear to have.
But just because twins share this small, cramped space doesn't mean they have identical experiences.
If one twin has a greater share of the placenta than the other, they get more nutrients and oxygen and grow at a faster rate.
The latest thinking is that all sorts of differences between twins start in the womb, it might even explain the difference between our next set of twins.
Bless us, O Lord, and these thy gifts which we are about to receive Amen.
Dillon and Daniel Cain are 12-year-old twins.
They're identical in every way except that four years ago, Daniel was diagnosed with attention deficit disorder, also called ADHD.
Even from the time that they were small, Daniel would talk incessantly.
Board stretch, you put your feet up against a board.
See, because I have long legs but short arms You know, for Dillon, he can never get a word in edgewise, Dillon's more of a thinker, he's so much more shy than Daniel.
Their mother, Lisa, couldn't understand how her identical twin boys could be so different.
At least 80% of the time, if one twin has ADHD the other will too, showing that genes play a very important role.
But rare pairs like Daniel and Dillon show that genes don't tell the whole story and they are essential to scientists investigating ADHD.
The reason for studying twins is that genetically they're the same person, genetically identical, so if you find a major difference between them, particularly in the one who is affected with the disorder, it's likely that that's due to other factors such as the environment.
So they're extremely invaluable in giving us some clues as to where we should be looking for environmental causes for very complex mental health problems.
Follow my finger with your eyes, not your head, OK? The environment here can include things like, you know, being in the womb, birth problems and things that happen very early in life, because ADHD starts roughly before the age of six.
There are certain events that can happen in the womb, one's called a twin-to-twin transfusion where instead of blood being shared equally it tends to go to one twin more than the other.
Interestingly enough in the case of Dan and Dillon, actually they were a case of twin-to-twin transfusion, so that might give us some idea as to some of the things that are happening in the womb that might be associated with later ADHD.
Touch my finger, touch your nose.
Touch my finger.
Good.
Touch my finger Now try it with the other hand.
It's thought that differences in blood flow and nutrients in the womb could be linked to the subtle differences in the structure of the twins' brains, revealed by MRI scans.
I think my brain's going to look smarter than Dillon's.
To the naked eye, the twins' brains look the same, but when scientists analysed results from a number of pairs, they found some interesting differences in one brain structure.
What we've found so far is that there's a certain structure in the brain and it's called the caudate, and we've found that this structure, the caudate, tends to be smaller in the twin who is affected by ADHD.
And that makes a lot of sense.
It might suggest that the looping of information around the brain is being affected by this smaller caudate deep, deep in the brain.
It seems subtle environmental differences even before we are born can play a part in shaping the person we'll become.
It's another new strand in that age-old debate, the balance between nature and nurture.
And while that debate may be evolving, it's still raging fiercely over the topic of sexual orientation.
Both my parents are straight, so when it comes to nature or nurture I think itI don't know that there's a real good answer for that.
I believe it's like a little bit of both, of how you're brought up and if you're born with it.
A lot of it is the way that you're brought up, the environment you're raised in has a lot to do with how you turn out sexually.
It's something in you that you know, from the second you're interested in any sex, you know what you're interested in.
Everybody says different things, some people says it's not, it's a choice, but I don't think it's a choice.
I could have been raised by wolves and still have been gay.
It doesn't matter.
Two identical twins who are desperate to resolve that nature/nurture debate are Mark and John Adams.
They hope it will finally explain their one striking difference.
So, we were always together.
Always.
Not any more, he's in LA, I'm in Kansas still, so Yeah, now there's just, just, hm.
Mark has settled down in Kansas to raise a family with his wife Jennifer, but things haven't been so straightforward for John.
I really didn't come to terms with my sexuality until well after college, not until I was 26, I believe, now I'm 34, and Mark, Mark brings up a good point which we've discussed many times, this whole nature versus nurture.
I can't believe that it would be nurture.
Especially when we grew up under the same roof and had the same friends and generally had the same interests, it's That's where I'm convinced.
That growing up here in Kansas, whenever they referenced gay people, it was men who were wearing dresses or were very effeminate.
When I started coming to terms with it, I knew in my mind that that's not who I was, I had no interest in, you know, putting on a dress or wearing lipstick or doing any of that sort of thing.
When John came out, the first person he told was his brother Mark.
When I came out to Mark it, it definitely brought us closer because he was, I knew after we had the conversation, which was actually very short, and I knew he would be, he's a, he's a champion of mine and has been my best friend and always will be I felt real sorry for you cos I I knew that we're the first of many that, that were that you were gonna tell and, and just watching you agonise and just telling me, I just felt sorry for you.
If he in fact chose to do this, be gay, then why would he choose to go through the agony of telling everyone, why, and, and go through all the prejudices that come with it, why would someone choose that? Studies have shown that identical twins are more likely to share the same sexual preference than non-identical twins.
This certainly suggests that there is a genetic component to sexuality.
But if it was just down to genes, then Mark would be gay too.
No-one has ever asked me if I'm gay because my brother is.
Clearly there's something else going on and it's being revealed by an exciting new area of science called epi-genetics.
Epi-genetics is the link between nature and nurture, it's between our genes and the environment.
And it'swe're in a very exciting time because we're just for the first time realised that actually the genes we're born with can be changed by our outside lifestyle and everything else.
In every cell of our bodies, we have chromosomes that are made up of spiralling DNA.
Every cell has exactly the same DNA, spelling out the same genes.
But not all genes are switched on all the time, they can be covered up by chemicals so that they're switched off or turned down.
These epi-genetic chemicals are what control our genes.
The relationship between the DNA sequence and the epi-genetic chemical is similar to that between sheet music and an orchestra conductor.
The DNA or genome is essentially a set of written instructions a bit like sheet music, but the epi-genetic chemicals are more like the conductor, who actually brings the music to life by telling the instruments when to come in and how loudly or softly they should play.
Just as different conductors may produce different sounds from the same piece of written music, different epi-genomes produce different appearance or behaviour from the same DNA.
To find out whether epi-genetics can explain why they're so different, the Adams brothers are taking part in a study at UCLA.
John is meeting Dr Sven Bocklandt who's coordinating the study.
John's brother Mark has already given his sample, as have 34 other pairs of twins who differ in their sexual orientation.
John is curious to find out what Dr Bocklandt has discovered so far.
So what we actually think is that it's not so much a matter of what genes you have, but which genes you use.
And there you and your brother are actually quite different, you both were once one embryo but once you split up in two, each developed in their own way, and so it might have been that you have, let's say the stray genes but you turned one off and that's why you're gay, or it might be that your brother got the gay gene, quote, unquote, as well, but he turned that one off and therefore he's straight.
So what we're trying to see is actually not what genes you have but how you use them.
So which genes are turned on and which one are turned off in your DNA.
Dr Bocklandt's research is at an early stage but he thinks epi-genetics could be very revealing.
But I think we're onto something.
We have, you know, we have data and it's all very new and we're still analysing it, but we find some genes that are really consistently different between gay guys and straight guys.
The differences are very small, so it's hard to tell right now whether they actually matter, we're just trying to get an idea, just trying to find a gene that plays a role in sexual orientation because so far we really don't have any idea what type of genes we're looking for.
Interesting.
Personally I think it's nature, I don't think my sexuality was defined by how I was raised or where I lived or that sort of thing, I definitely think it's because of biological reasons or my DNA or, or something.
Epi-genetics isn't just helping scientists understand sexual orientation, it's shedding new light on the whole nature/nurture debate and could finally help to explain how our genes and environment combine to make us who we are.
Once again, differences between identical twins make them perfect subjects for scientists studying how our environment can turn genes on or off.
Over time, and in response to maybe just random events or environment, the epi-genetic profile of any given individual will change.
Now the power of identical twins is we can actually measure this change, because these two individuals are genetically identical, we can measure how epi-genetically different they are.
So far, Xand has been successful in his mission to show that he's a product of his environment rather than a slave to his genes, but after a year of living very different lifestyles, could there now be real genetic differences between him and his twin Chris? A year ago, Dr Rakyan took DNA samples from Chris and Xand, now they're having blood taken again to see if there are any changes.
I sometimes scream.
It's good, you can scream, I will tell you when to scream when I put the needle in.
We both feel it each time you do it, so it's double.
Twice as much pain.
Say ahh.
Ahh.
I'm just about to put the needle in.
Hey.
He's fainted.
Are you OK? No, I'm fine, I'm fine, don't worry.
Once the blood has been taken, the scientists extract the DNA from the white blood cells.
The DNA is then treated with a chemical which reacts with the epi-genetic markers.
These genes show up green, while the genes that are unmodified show up red.
Once their samples have been analysed, Chris and Xand meet Dr Rakyan to get the results.
So this is a figure of all the chromosomes in the human genome, and marked here are the changes we've observed in these chemical modifications over the course of one year.
The blue triangles are the regions where Chris has acquired more of these chemical modifications, whereas the red triangles are the regions where you, Alexander, have acquired more of these chemical modifications.
Overall, Chris, it looks like you have acquired more of these chemical modifications.
And what about some specific changes, can you tell what genes have been changed? Sure.
As an example we could focus in on one chromosome, so let's take chromosome four, for example.
The changes that have occurred only in you, Alex, are in red and the changes that have occurred in Chris are shown here in blue.
So the, the blue bar is much, much bigger in me from 2008 to 2009, whereas Xand has stayed pretty much the same.
That's correct.
So I'm much more chemically modified in that gene than he is? That's right.
Although it's the same gene we've modified it differently? Yeah.
And that means that it's likely to be expressed differently, the gene will be turned turn or turned off? Yes.
And do we know what those two genes do then? We do.
So we've had a quick look at the function of these genes and they seem to be involved in metabolism.
That's interesting because there seems to be a metabolic difference between us at the moment, he's much heavier and we've had a metabolically different year, haven't we? I've had a very active year, I've gone to Africa and gone to the Arctic and been very active, busy job, cycling to work, and as far as I can tell you've done nothing but eat all year and allegedlyand allegedly did read some books.
And work.
Yeah.
Right.
This is the final piece of the puzzle.
Although Chris and Xand are genetically identical, their lives have continually affected the way their bodies work, these changes have, in turn, modified the way their genes are expressed.
Thanks to the different experiences they've had in their lives, Chris and Xand are now epi-genetically unique.
Epi-genetics is so revolutionary that it's changing the way that scientists like Professor David Leslie are thinking about some of the world's most widespread and debilitating diseases.
I started off as a geneticist but, because I've been studying twins, I've now become a non-geneticist, because I know it's not the genes that give you these diseases, it's the environment that gives you the diseases in interaction with the genes.
So it's that interaction which is important, and that's why epi-genetics is so important, because it's a fingerprint of that interaction.
One such disease is Type 1 diabetes, it affects 20 million people worldwide.
Sasha Jacombs has been living with diabetes since she was five years old.
If her blood sugar drops too low, she has fits.
I've had several fits when I've gone so low I just like start like She screams, she doesn't remember it but they're the scariest thing ever.
No.
I zone out and I won't know anything and then I'll wake up and everyone's pouring sugar on me and I'm like "What?".
The most scariest thing in my life seeing Sasha with a fit, cos she just screams and flails and it's horrible, and I never thought she was gonna come out of it.
For Sasha and Becky's parents, Jackie and Terry, it's the nights that are particularly hard.
For the last ten years we, one of us has had to get up in the night, so she normally gets checked at probably sometime between 11 and 12, and then one or other of us will get up at half past two in the morning roughly, to check, and then I usually get up at half past six each morning to check, so, and that's that's normal life now.
Sasha's identical twin sister, Becky, doesn't suffer from diabetes but the disease still affects her.
Because of Sasha's diabetes, I probably worry about her more than she's ever gonna worry about me, and I do think about her probably more than most people think about another sibling.
So I still have quite a high chance of developing it myself, but I probably tend not to think about that because actually that's kind of depressing.
Professor Leslie has collected DNA samples from twins where one has diabetes and the other doesn't to look for epi-genetic markers.
We've been able to identify a series of genes which have these epi-genetic markers, which are associated with the disease in the diabetic twin, but are not found in the non-diabetic twin.
These epi-genetic markers could help diagnose and treat diabetes much earlier.
We're developing now our various vaccination programmes, which have been successful in limiting the disease process in people with the disease and obviously would be probably more successful if we were able to treat people before they developed the actual clinical diabetes.
The latest medical advances achieved through epi-genetics do go way beyond vaccination and diagnosis.
Now epi-genetic treatments for life-threatening illnesses are reaching the final stages of clinical trials.
One epi-genetic therapy offers new hope for patients like Rajesh, diagnosed with MDS, an early form of adult leukaemia.
We were just shocked with the diagnosis, it was like the world come standstill because if this condition got worse going to leukaemia and then you're looking at what - a life expectancy of 18 months.
All the time I was in bed because I was not feeling 100% at all, I was not - I just didn't want to do do anything, just my body won't let me do anything.
This revolutionary new treatment is being trialled at King's College Hospital in London.
Epi-genetic therapy is where you give medication that modifies the genes which are structurally normal but those genes are not properly expressed.
So the drug reprogrammes these cells so that they are able to produce certain proteins normally which then tell the cell not to divide as a leukaemic cell again.
After a few months' treatment, Rajesh now has a normal haemoglobin level.
The next stage will be to do a bone marrow transplant, so that he's cured of his disease and that's what we are planning to do.
But this particular drug and this form of therapy definitely allowed us to give him the treatment without having any side effects, like any chemotherapy side effects.
Well, he looks so much better now, the little one keeps saying, "Mum, you've got a problem taking Daddy to the hospital, "there's nothing wrong with him, he's fine.
" And I just wish that everything comes back to normal, we can go back into a normal life.
Its a very exciting area because for the first time, we are looking at not quite killing the leukaemic cell but we are able to reprogramme the cells so that they can go to functionally competent cells.
The main area where these drugs are being looked at and will probably have a very important role to play, will be cancer.
Epi-genetics is at the cutting edge of modern medicine.
It's one of the most exciting new areas of science, helping us to understand how diseases are caused and how they might be treated, and thanks to twins, we're gaining ever greater understanding of what makes us alike, what makes us different and what makes us who we are.
They've helped to reveal that some of the most profound influences on us occur between conception and birth and that the genes we inherit from our parents don't work on their own but are controlled by epi-genetics.
Epi-genetics may even influence the genes that control normal development in the womb, turning some cells into brain cells, bone or skin and occasionally triggering random and unexpected differences that could set identical twins on different paths before they're even born.
Colin and Hermie's twin boys have been in the womb for 36 weeks, long enough for significant differences to develop.
Now they're going to be delivered by Caesarean section.
Yeah? Right.
Oh, no, I'm fine.
This is the right twin, I think.
Can I havethank you very much.
Hello.
Hello, we've got, ooh, that's the first twin, that's the right one.
OK? There we go.
Wonderful, that's the second twin.
Just hand him a minute.
Thank you.
Congratulations, well done.
I just can't believe one minute they were inside and then now, you know, they're just here.
They're so tiny and perfect.
Although their shared DNA will make these twin boys incredibly similar in so many ways, their destinies are not written in their genes.
By living different lives, they will influence which of their genes are turned on or off, shaping the people they become.
As nature's clones, twins will continue to enlighten us, and perhaps by the time babies Finn and Max have grown up, we'll understand even more clearly what really makes us who we are.
As nature's clones, they're without doubt fascinating to us and to each other.
The minute we saw the twins, we were looking at them and comparing.
I think it's amazing seeing loads of twins because I think other twins are weird.
But they're not just intriguing to look at.
These genetically identical individuals are invaluable to scientists who are desperate to unravel the nature/nurture debate - are we born or are we made? We always think of them as slight oddities of nature, but they can help you and I to uncover really important diseases that are affecting us all.
Last time we met identical twins who were remarkably similar, not just in the way they look but in their personalities and their approach to life.
I've tried to commit suicide quite a few times.
I was actually going to die if I kept going the way I was going.
Despite leading very different lives on opposite sides of the world, Ian and Paul suffered almost identical heart conditions.
After all this time of doing the right thing, I find out that I'm no different from my brother.
Even twins like Mia and Alexandra, who were growing up on separate continents, have loads in common.
That look right there, that was Mia.
Twin doctors, Chris and Xand Van Tulleken discovered that their genes make them identical in some surprising ways, from how they vote, to their maths ability and whether or not they'll take risks.
I'm a bit worried about him.
Are you worrying about me? I don't care at all about you.
I'm worried about my feet getting cut.
But having identical DNA doesn't make twins exactly the same, as Chris and Xand discovered in a test for pain tolerance.
I was wincing at the beginning but now I'm dying.
It's these intriguing differences between identical twins that we're exploring in tonight's programme.
Do you and I behave differently? The answer is yes, we do.
I think the answer to that is no we don't.
We'll find out how dissimilar Chris and Xand actually are and we'll meet other identical twins who are incredibly different.
So even though she was born five minutes ahead of me, I'm ten years older than her? Including fat and thin twins, Noora and Miia in Finland.
Oh, my god, I'm going to be as heavy as she is and I have to wake up now.
And Mark and John in America who have one striking difference.
No-one has ever asked me if I'm gay because my brother is.
We'll discover that although our genetic make-up is fixed at conception, the environment can start to shape us even before we're born.
And we'll explore one of the most exciting new areas of science, revealing how our lifestyle can affect the actual workings of our genes.
SIRENS SOUND All children are fun, but twins are twice as entertaining and double the trouble.
People often say to me, "so who's the good twin and who's the evil one?" I'll say Tal and she'll say Cel.
Each year in the UK, identical twins are born to around 4,000 couples.
Would you like to hear the babies? In just a few months, Hermie and Colin Willets will join them and their son Thomas will have two new identical baby brothers to play with.
It was very exciting when Hermie told me she was pregnant, I mean we were just bracing ourselves for one and then we found out that it was two, didn't we? We went for quite an early scan so it was around eight weeks.
Yeah, well, have a listen then, tell daddy what does it sound like? Boom, boom.
We were just more concerned about them finding a heartbeat and she said, "Here's a heartbeat" and showed me.
Then she looked again and said, "Yeah, that's it, there's two.
" I don't think Colin spoke then for the rest of the session.
No, it's one of the only times in life, and people say that they were speechless, but I genuinely was speechless for about 20 minutes, I really didn't know.
You were almost in hysterics, weren't you? I genuinely was speechless for 20 minutes.
We'll be following Hermie's very special pregnancy throughout this programme.
It started out in exactly the same way as her first pregnancy.
A single egg was fertilized by a single sperm.
But this time, the embryo inexplicably divided at some point in the first week to form two identical twins, something that's always been considered a scientific phenomenon.
The two new babies have identical DNA, but throughout their lives, differences will emerge, and this is like gold dust to scientists.
For years, scientists have been trying to work out how much we're all shaped by nature, our genes, as opposed to nurture, our environment.
Studying twins who share the same genes is one of scientists' unique ways of exploring this question.
In the next stage of their journey, identical doctors Chris and Xand want to see whether their own differences can help them to find answers.
Do you have freedom in your life to make decisions to change the way you are and the way you live? Xand wants to prove that their different experiences have shaped them more than their identical genes.
We deal with people in a subtly different way.
You're quite confrontational, quite straightforward with people.
I tend to be more conciliatory and relaxed.
It's a different thing.
If I So you're saying that we behave Look at how confrontational you're being.
To prove his point, Xand is taking his brother back to St Thomas's for a full examination to reveal all their physiological differences.
They're being tested for bone density, pain tolerance Ow! .
.
and lung capacity Right, keep going.
.
.
as well as height, weight and grip strength.
Keep squeezing harder, harder, harder, harder, harder, harder, harder, stop.
OK.
Well done.
Yours was 65 kilos.
Really? Yeah, and yours was 39 kilos.
What? Give me that one, give me that one - there's got to be some problem with the machine.
OK, we'll do best of five.
The Department of Twin Research has run these tests for nearly 20 years on thousands of twins.
Professor Tim Spector has met many of them.
Today he's got some interesting results for Chris and Xand.
The key statistic here is the percentage fat difference between you.
Xand has 30 and you have 19.
Oh, that's terrible, isn't it? Which is a huge difference.
Yeah, that's terrible, isn't it? So he's actually at a very good level and you are unfortunately A disgrace.
The wrong side.
A disgrace to your genes.
That is bad, isn't it? A disgrace to MY genes is more to the point.
With 11% more body fat, Xand weighs in 15 kilos heavier than Chris.
That's very unusual.
Most identical twins are incredibly similar in weight, rarely more than three or four kilograms apart.
In fact, studying twins has shown that just like height and eye colour, our weight is definitely influenced by our genes.
But genes are not the whole story.
Puzzled by their weight difference, Chris and Xand want to know whether different lifestyles could be the cause, so they're going to do a study of their own.
So are you still fat? I'm not any slimmer than I was the last time that I saw you.
Right, so still fat then? Pretty much.
How's that working out for you at Harvard? It's all right, I don't have to move much so it's quite nice.
I'll bet it is.
It would be quite interesting to know how much exercise and how much moving around we're doing in a week compared to one another, and also to keep some sort of food diary to see if you really are eating less than me.
Step measurement's quite a good way of just assessing the differences in activity in our day.
It won't give us an absolute calorific value, but it's a good comparator, isn't it? For the past year, Xand has been living in Harvard, where he's being doing a degree and writing a book.
As a result, he spends a lot of time sitting in libraries and at his desk.
In contrast, Chris cycles almost everywhere.
His daily commute to and from the hospital where he works is five miles, and once he gets there, he's on his feet all day seeing patients.
Some days he barely has time for lunch.
But are these lifestyle differences really big enough to outweigh the influence of their identical genes? From the pedometers, every month you're doing the equivalent of walking from London to Bristol, is that right? Yes, and cycling from London to Manchester.
And doing the cycling as well.
And what were you doing? Well, I'm not really getting outside the M25.
I'm getting from London What are you doing in a day? I'm getting from the middle of London to the outer edges of London.
My shoes don't fit, I've got chafing on my inner thighs from all the fat.
Yeah.
So you're eating, we reckon, about 12 more hamburgers a month than me, the calorific equivalent of about 12 hamburgers more, 12 large hamburgers.
It doesn't seem that much, but think of the 12 hamburgers piled on the plate.
Piled around your waist.
That's the problem.
The 12 hamburgers go right there, don't they? Certainly in my case, my weight gain is environmental, not genetic.
But twin studies are revealing that Xand can't blame his lifestyle alone for his weight gain.
It's estimated that a billion people worldwide are overweight - that's one-sixth of the earth's population.
In fact, the World Health Organisation claims that obesity is fast becoming as big a problem as malnutrition.
So it's crucial for scientists to understand exactly what causes us to put on weight.
Once again, identical twins are providing some answers to this very common problem.
And that's, may I say it aloud? Yeah.
77.
2 kilograms.
OK.
Noora and Miia Simola are only 24, but already Noora weighs 17 kilograms more than Miia.
They're taking part in research by the University of Helsinki to understand what causes us to put on weight.
Where are we Noora right now? We are at strenuous.
Twins like Miia and Noora provide detailed information about their activity levels throughout their lives.
One of our important findings is that teenage years are very important in terms of what habits you then follow later on in your life.
So if you become physically inactive, that tends to persist and tends to be so in the adult life as well.
This is what happened to Noora.
When she went to college, she stopped eating healthily and exercised less.
I was studying till late night and didn't have the strength to do anything afterwards.
I just started walking and jogging alone in the same places.
Yes, because you have the time in the evenings and you were alone and doing anything.
But I have been with my boyfriend seven years, that's also one thing when you kind of settle down, you don't even have to care about your looks that much any more because you have this one guy.
You're not picking up some guy.
Yeah.
Noora is living proof of a new discovery helped by the study of twins.
Scientists now know that putting on weight actually changes the way our fat cells work.
We see very clearly that the obese co-twin's fat tissue is less efficient, it's not using energy very well.
Whenever the people eat, it just stores the fat in the fat tissue and this, of course, then means that weight loss might be more difficult and putting on weight would be very easy.
The discovery explains why putting on weight is easier than losing it.
And it's helping to show why some people stay the same weight no matter what they eat.
The key is to understand how our lifestyle interacts with our genes.
It seems that twins who differ widely in weight share food sensitivity genes which trigger rapid fat buildup when either of them eat excess food.
Twin studies are helping scientists identify these genes.
We have found evidence that one of the genes involved in appetite control called ghrelin is in fact differently distributed in the discordant pairs where one is obese, one is lean.
Professor Kaprio's conclusion is that our appetite is determined by our genes.
Genes that increase our appetite and cause us to put on weight easily were probably an advantage in times of famine.
The problem for people like Noora is they're never short of food.
As Noora's twin, Miia shares the same genes, so she will really have to watch her diet if she wants to stay slim.
I think it's a good thing that she is heavier than me, because when, when I was 63 kilos and I saw that she was a bit heavier than I, I was like, "Oh my god, "I'm going to be as heavy as she is and I have to wake up now and I have "to get the weight down because it's so much harder for her.
" So it was good the wake-up call for me that I could see the same body as mine and compare it to mine.
Twin studies have shown that different lifestyles can affect the way our genes shape our bodies.
It's not just how we put on weight but also how we age.
The hands of time touch everyone, but these two identical twins are concerned they may not be ageing at the same rate.
Sue and Shelagh Wright don't look the same any more.
But as children, they were so similar, even they can't tell who was who.
That one is me because that one I think looks more intelligent.
Although this one is looking rather cute and studying the plant.
Maybe that, I don't know.
Both Shelagh and Sue married their Mr Rights.
But sadly Sue didn't live happily ever after.
Her husband was diagnosed with a very serious illness.
With Huntingdon's Disease, my husband actually had the severe psychiatric symptoms.
He became violent and would assault me, so I had to leave the marital home for my own safety.
Sue got involved with an online support group for Huntingdon's, but this wasn't always a good thing.
Because it's such a grim disease, people choose suicide, so I would often be trying to talk people out of suicide.
So being a smoker, I would sit there at my desk puffing away far more than probably would have been the norm in other circumstances.
It's pretty stressful.
It can have its rewards too.
I've always said, for whatever reason, life's been very kind to me and not nearly as kind to my twin.
Shelagh has always been sympathetic to Sue's plight, but can't relate to some of her lifestyle choices.
I don't know why Sue started smoking, but I had one cigarette and turned green at the gills and decided it wasn't for me.
I decided not to abuse myself in that way.
And then because I have been at work for much longer, I've been able to keep more physically active.
To find out whether these different life experiences have affected how old they look, Sue and Shelagh are visiting the L'Oreal Laboratories in Paris.
The scientists here make a very detailed analysis of Sue and Shelagh's skin measuring differences in hydration, elasticity and wrinkle depth to determine how they're both ageing.
I'm just hoping my wrinkles won't look like Mount Everest and the Grand Canyon.
By analysing the skin of 1,000 twin pairs, the researchers hope to work out exactly which lifestyle factors make us all age.
We can make a sort of a weighting of different factors like the sun, like tobacco, like food, like stress, from professional stress to family stress or sickness.
All these thing can induce some rapid ageing.
They hope to prove that your life is quite literally written in your face.
Having gone through the whole range of tests, it's time for Sue and Shelagh to find out who has the older-looking skin.
The first thing I have to say is you have a very young skin in term of mechanical properties, you have very young skin.
Now, in term of clinical aspect, the ageing process When we look at a replica, we can see a light increasing depth of your wrinkle, Shelagh, in comparison with Susan.
And when we calculate your apparent age with the different clinical scores, we can see that you look four years younger than your sister.
Oh, you didn't anticipate that.
I'm delighted that I seem to have come out better on this when I anticipated coming out worse.
But perhaps it could be a problem of a body mass index of weight.
The fact that Sue is carrying extra weight seems to outweigh the effects of smoking and stress, making her skin at least appear younger.
At a certain age, many women feel the need to choose between their body and their face, because losing weight can make you look older.
Don't really want to end up looking like a bloodhound.
Sue's surprising result shows how complex the relationship between the environment and genes is.
But the signs of ageing are more than skin deep.
They're found in every cell in our body.
Our cells continually divide and with each separation, the chromosomes are duplicated.
But each time this happens, part of the chromosome tip, called the telomere, gets shorter.
So the length of our telomeres shows us how fast our cells are ageing.
So, are Shelagh and Sue's biological clocks ticking at the same rate? They're hoping Professor Spector at the Department of Twin Research will have some answers.
Compared to the average woman, both of you are actually doing pretty well telomere-wise, but there is a ten-year biological difference between you.
You've got the longer telomeres, you've got the shorter ones.
So even though she was born five minutes ahead of me, I'm ten years older than her in my body.
So, that's right, you know, these are only very rough approximations and we found in our studies using thousands of people, it shows average most of the differences between a smoker and a non-smoker, or someone who's fat and someone who's thin is around eight years' difference, and similarly someone in a high social class, low social class, between eight and ten years' biological difference.
So it makes sense that once you add up these differences between you two you get a similar sort of result, of this, this difference between you that actually, you know, you're doing particularly well even much higher than the average, and you are ten years behind, if you like.
Though Sue's skin appears younger, her experiences in life have aged her body cells faster than Shelagh's, despite sharing identical genes.
Cellular ageing leads to more than just wrinkles - it increases the risk of illnesses like osteoporosis, arthritis and cancer.
It shows that in combination with the genes you're born with, your environment at every stage of life can have a major impact on how well your body will work.
With this in mind, Xand wants to find out if events in his childhood could have left him more prone to weight gain than Chris.
You kept getting these punctured eardrums and that started at quite a young age, and that did not happen to Christopher, and eventually they put grommets in the ear which was supposed to clear it.
They're supposed to drop out after a year and yours didn't.
So we had to have them taken out.
And then you couldn't swim.
Christopher, in the meantime, was swimming so that made a difference at a young age, and then as a result of that, you had to have your tonsils out or your adenoids orI don't know.
When I had my tonsils out, I was told I could eat whatever I wanted afterwards and I was really looking forward to that, and I was told ice cream would be nice, and I didn't want ice cream, I wanted pork pies.
I remember this really clearly.
I was told I could have as many pork pies as I want, and I must have eaten 2o pork pies a day or something.
The little ones, the little ones.
And I'd completely forgotten this until you said it and I remember I think you sort of said, "Well, it's not quite what most people have for tonsillitis.
" That's right, so even then we had the circumstances of Chris busily swimming and probably eating carrots and Xand in hospital No, you were.
.
.
.
with his television and eating pork pies.
Perhaps their different exercise levels and attitudes to food as children hold the key.
Did they establish a lasting pattern that's causing Xand to gain weight more easily than Chris? The idea that small chance experiences in childhood can have a lasting effect on our lives is one that intrigues scientists like Doctor Kathryn Asbury.
With identical twins it's easiest to think of it as parallel universes, you've got this same set of DNA going out into the world and bumping into slightly different people, slightly different experiences.
Someone might fall down in the playground and break their leg and be off school for six weeks and that might make a difference to the friendships they make and how they perform in school.
And it's these tiny experiences, these tiny parts of life that add up to make us who we are, I think, along, alongside our genes.
Some of these chance events can have a positive impact on our lives, but others can have a much bigger, more devastating effect.
Saturday you've got ballet, then the party.
Olivia and Isabella Murphy look and act like any other six-year-old girls.
For their early years, Olivia was almost indistinguishable from her identical twin sister.
But then she went through a terrible ordeal.
We're both the same size but I was poorly, and I the medicine made me go small.
Around about the age of two and a half, I noticed Olivia hadn't been feeling well for quite a while, and decided that I would take her to the GP for a blood test.
She was looking very pale and anaemic, really sleepy.
They then came back and said, oh, unfortunately the reason why Olivia is so anaemic is that she has the childhood cancer leukaemia, and yeah, that was in July, and straight away we were sent up to Great Ormond Street.
To tackle the leukaemia, Olivia was put on an intensive course of chemotherapy.
On the chemotherapy, Olivia lost her hair so straight away, they lost to me their little twinness.
A lot of the time if I had both girls they would say, ooh, you have one of each, a boy and a girl, and sometimes I would say, "No, actually, this is a girl," and sometimes I would just let it ride.
She had no hair but it's not funny.
Cos a girl having no hair, it's because she was poorly and As Isabella was getting taller, healthier and Isabella Olivia lost loads of weight and for quite a long time she also couldn't walk and she was getting smaller and frailer.
And she thought I was dead.
I thought, yeah, but I found she was gonna, she was nearly gonna die.
Olivia underwent two years of treatment for leukaemia, which took its toll on her and her twin.
It was very hard for Isabella, definitely, because she'd been used to having her sister to play with and all of a sudden she didn't have that any more, and she didn't have me around as much any more, and every now and then I do catch them talking about it.
Isabella would say, "You've got to spend lots of time with Mummy "in hospital", and Olivia would say, "Well, you got taken to Legoland.
" So, yes, for everyone involved it was, it was quite a tough time.
Breathe in deep.
The fact that Olivia developed leukaemia was obviously a tragedy for the family, but as her twin sister Isabella remained healthy, it was a great opportunity for scientists to explore why.
It has long been suspected that there's a genetic basis to leukaemia but exactly how it started in Olivia was a mystery.
Quite often in twin pairs that we've studied for many years, both the twins will have leukaemia pretty much the same time, they share the same disease.
So that begs the question what's going on in this twin pair, Olivia and Isabella.
Now, we think it's probably in a way just bad luck but something probably triggers the disease and all the evidence we have suggests it's probably infection, so we suspect Olivia had an infection.
We know she had tonsillitis of some kind, and it was probably that that triggered the leukaemia and her sister escaped because she didn't have that particular infection.
But tonsillitis doesn't cause leukaemia by itself.
With funding from Leukaemia Research, Professor Mel Greaves compared the girls' genes, searching for mutations triggered by Olivia's infection to cause leukaemia.
We first of all characterised Olivia's blood and the types of mutations she has in her blood cells, then we went to Isabella's blood, and what we were able to find are low levels of leukaemic cells having a single mutation, in contrast to her sister Olivia, whose leukaemic cells have five mutations.
Born with that first mutation, Isabella will always face the risk of developing leukaemia just like her twin.
But, fortunately, both she and Olivia have blood tests every six months to keep an eye on this.
Obviously, I briefed them on the fact that they will have to give blood and I don't think they're too pleased, but, after a little bit of encouragement, they're OK.
Thanks to Olivia and Isabella, scientists are now able to identify pre-leukaemic cells before the disease has started.
It gave us unique access for the first time to the early stages in the evolution of the disease, where, in essence, Isabella has the fossil evidence of how this disease evolves and develops, so it was a unique opportunity to look at the earliest stages of the disease that we couldn't otherwise have had.
And what's more, scientists are discovering that these very early stages of leukaemia even start before birth.
Identical twins, including, the girls, Isabella and Olivia, share a single placenta in mum's womb when they're developing as babies, and the consequence of that is they actually share each other's blood, so leukaemia might start before birth with a mutation of the DNA.
So leukaemia isn't simply inherited in your genes, it's a complex disease caused by a combination of chance environmental effects and our DNA.
Twin studies continue to reveal how the environment affects us as adults, as children, and even before we are born.
Images like these, produced with cutting-edge ultrasound technology are giving researchers an unprecedented view of babies' lives inside the womb, and they're helping to reveal how conditions in the womb can shape our development much later in life.
Today is an important chance for Colin and Hermie Willits to see how their unborn twins are developing.
Hermie very nice to meet you, and Colin.
Hi.
Right.
Do come along to the scanning room.
Professor Campbell is a pioneer of 4D ultrasound and over the years has seen thousands of pregnancies.
We have to put a layer of gel so that all the air pockets in the skin, but I hope it's not cold.
Is it not cold? Just a little.
So one head down, the body at the, on the left, one head up and the body on the back is on the right.
OK.
OK, so this is twin one.
And there's the little face, that's the baby that's, looking down.
What a good-looking baby.
Yeah, and it's amazing to see their expressions.
Yeah.
It's just quite nice to be able to, to see them as they are and to say hello, really.
I think it's making it, a little bit more real, I suppose.
I think I'm still in denial.
So this is twin two, and there, and this is the heel of the other one.
So these are the legs of twin one.
This is the hand of twin two.
So twin two may be going to hold the leg of twin one at any, any second I think.
The twins are so close together it looks as if twin two could reach out and hold the leg of twin one.
Contact between twins might not be intentional, but this closeness could be the start of that special bond that so many twins appear to have.
But just because twins share this small, cramped space doesn't mean they have identical experiences.
If one twin has a greater share of the placenta than the other, they get more nutrients and oxygen and grow at a faster rate.
The latest thinking is that all sorts of differences between twins start in the womb, it might even explain the difference between our next set of twins.
Bless us, O Lord, and these thy gifts which we are about to receive Amen.
Dillon and Daniel Cain are 12-year-old twins.
They're identical in every way except that four years ago, Daniel was diagnosed with attention deficit disorder, also called ADHD.
Even from the time that they were small, Daniel would talk incessantly.
Board stretch, you put your feet up against a board.
See, because I have long legs but short arms You know, for Dillon, he can never get a word in edgewise, Dillon's more of a thinker, he's so much more shy than Daniel.
Their mother, Lisa, couldn't understand how her identical twin boys could be so different.
At least 80% of the time, if one twin has ADHD the other will too, showing that genes play a very important role.
But rare pairs like Daniel and Dillon show that genes don't tell the whole story and they are essential to scientists investigating ADHD.
The reason for studying twins is that genetically they're the same person, genetically identical, so if you find a major difference between them, particularly in the one who is affected with the disorder, it's likely that that's due to other factors such as the environment.
So they're extremely invaluable in giving us some clues as to where we should be looking for environmental causes for very complex mental health problems.
Follow my finger with your eyes, not your head, OK? The environment here can include things like, you know, being in the womb, birth problems and things that happen very early in life, because ADHD starts roughly before the age of six.
There are certain events that can happen in the womb, one's called a twin-to-twin transfusion where instead of blood being shared equally it tends to go to one twin more than the other.
Interestingly enough in the case of Dan and Dillon, actually they were a case of twin-to-twin transfusion, so that might give us some idea as to some of the things that are happening in the womb that might be associated with later ADHD.
Touch my finger, touch your nose.
Touch my finger.
Good.
Touch my finger Now try it with the other hand.
It's thought that differences in blood flow and nutrients in the womb could be linked to the subtle differences in the structure of the twins' brains, revealed by MRI scans.
I think my brain's going to look smarter than Dillon's.
To the naked eye, the twins' brains look the same, but when scientists analysed results from a number of pairs, they found some interesting differences in one brain structure.
What we've found so far is that there's a certain structure in the brain and it's called the caudate, and we've found that this structure, the caudate, tends to be smaller in the twin who is affected by ADHD.
And that makes a lot of sense.
It might suggest that the looping of information around the brain is being affected by this smaller caudate deep, deep in the brain.
It seems subtle environmental differences even before we are born can play a part in shaping the person we'll become.
It's another new strand in that age-old debate, the balance between nature and nurture.
And while that debate may be evolving, it's still raging fiercely over the topic of sexual orientation.
Both my parents are straight, so when it comes to nature or nurture I think itI don't know that there's a real good answer for that.
I believe it's like a little bit of both, of how you're brought up and if you're born with it.
A lot of it is the way that you're brought up, the environment you're raised in has a lot to do with how you turn out sexually.
It's something in you that you know, from the second you're interested in any sex, you know what you're interested in.
Everybody says different things, some people says it's not, it's a choice, but I don't think it's a choice.
I could have been raised by wolves and still have been gay.
It doesn't matter.
Two identical twins who are desperate to resolve that nature/nurture debate are Mark and John Adams.
They hope it will finally explain their one striking difference.
So, we were always together.
Always.
Not any more, he's in LA, I'm in Kansas still, so Yeah, now there's just, just, hm.
Mark has settled down in Kansas to raise a family with his wife Jennifer, but things haven't been so straightforward for John.
I really didn't come to terms with my sexuality until well after college, not until I was 26, I believe, now I'm 34, and Mark, Mark brings up a good point which we've discussed many times, this whole nature versus nurture.
I can't believe that it would be nurture.
Especially when we grew up under the same roof and had the same friends and generally had the same interests, it's That's where I'm convinced.
That growing up here in Kansas, whenever they referenced gay people, it was men who were wearing dresses or were very effeminate.
When I started coming to terms with it, I knew in my mind that that's not who I was, I had no interest in, you know, putting on a dress or wearing lipstick or doing any of that sort of thing.
When John came out, the first person he told was his brother Mark.
When I came out to Mark it, it definitely brought us closer because he was, I knew after we had the conversation, which was actually very short, and I knew he would be, he's a, he's a champion of mine and has been my best friend and always will be I felt real sorry for you cos I I knew that we're the first of many that, that were that you were gonna tell and, and just watching you agonise and just telling me, I just felt sorry for you.
If he in fact chose to do this, be gay, then why would he choose to go through the agony of telling everyone, why, and, and go through all the prejudices that come with it, why would someone choose that? Studies have shown that identical twins are more likely to share the same sexual preference than non-identical twins.
This certainly suggests that there is a genetic component to sexuality.
But if it was just down to genes, then Mark would be gay too.
No-one has ever asked me if I'm gay because my brother is.
Clearly there's something else going on and it's being revealed by an exciting new area of science called epi-genetics.
Epi-genetics is the link between nature and nurture, it's between our genes and the environment.
And it'swe're in a very exciting time because we're just for the first time realised that actually the genes we're born with can be changed by our outside lifestyle and everything else.
In every cell of our bodies, we have chromosomes that are made up of spiralling DNA.
Every cell has exactly the same DNA, spelling out the same genes.
But not all genes are switched on all the time, they can be covered up by chemicals so that they're switched off or turned down.
These epi-genetic chemicals are what control our genes.
The relationship between the DNA sequence and the epi-genetic chemical is similar to that between sheet music and an orchestra conductor.
The DNA or genome is essentially a set of written instructions a bit like sheet music, but the epi-genetic chemicals are more like the conductor, who actually brings the music to life by telling the instruments when to come in and how loudly or softly they should play.
Just as different conductors may produce different sounds from the same piece of written music, different epi-genomes produce different appearance or behaviour from the same DNA.
To find out whether epi-genetics can explain why they're so different, the Adams brothers are taking part in a study at UCLA.
John is meeting Dr Sven Bocklandt who's coordinating the study.
John's brother Mark has already given his sample, as have 34 other pairs of twins who differ in their sexual orientation.
John is curious to find out what Dr Bocklandt has discovered so far.
So what we actually think is that it's not so much a matter of what genes you have, but which genes you use.
And there you and your brother are actually quite different, you both were once one embryo but once you split up in two, each developed in their own way, and so it might have been that you have, let's say the stray genes but you turned one off and that's why you're gay, or it might be that your brother got the gay gene, quote, unquote, as well, but he turned that one off and therefore he's straight.
So what we're trying to see is actually not what genes you have but how you use them.
So which genes are turned on and which one are turned off in your DNA.
Dr Bocklandt's research is at an early stage but he thinks epi-genetics could be very revealing.
But I think we're onto something.
We have, you know, we have data and it's all very new and we're still analysing it, but we find some genes that are really consistently different between gay guys and straight guys.
The differences are very small, so it's hard to tell right now whether they actually matter, we're just trying to get an idea, just trying to find a gene that plays a role in sexual orientation because so far we really don't have any idea what type of genes we're looking for.
Interesting.
Personally I think it's nature, I don't think my sexuality was defined by how I was raised or where I lived or that sort of thing, I definitely think it's because of biological reasons or my DNA or, or something.
Epi-genetics isn't just helping scientists understand sexual orientation, it's shedding new light on the whole nature/nurture debate and could finally help to explain how our genes and environment combine to make us who we are.
Once again, differences between identical twins make them perfect subjects for scientists studying how our environment can turn genes on or off.
Over time, and in response to maybe just random events or environment, the epi-genetic profile of any given individual will change.
Now the power of identical twins is we can actually measure this change, because these two individuals are genetically identical, we can measure how epi-genetically different they are.
So far, Xand has been successful in his mission to show that he's a product of his environment rather than a slave to his genes, but after a year of living very different lifestyles, could there now be real genetic differences between him and his twin Chris? A year ago, Dr Rakyan took DNA samples from Chris and Xand, now they're having blood taken again to see if there are any changes.
I sometimes scream.
It's good, you can scream, I will tell you when to scream when I put the needle in.
We both feel it each time you do it, so it's double.
Twice as much pain.
Say ahh.
Ahh.
I'm just about to put the needle in.
Hey.
He's fainted.
Are you OK? No, I'm fine, I'm fine, don't worry.
Once the blood has been taken, the scientists extract the DNA from the white blood cells.
The DNA is then treated with a chemical which reacts with the epi-genetic markers.
These genes show up green, while the genes that are unmodified show up red.
Once their samples have been analysed, Chris and Xand meet Dr Rakyan to get the results.
So this is a figure of all the chromosomes in the human genome, and marked here are the changes we've observed in these chemical modifications over the course of one year.
The blue triangles are the regions where Chris has acquired more of these chemical modifications, whereas the red triangles are the regions where you, Alexander, have acquired more of these chemical modifications.
Overall, Chris, it looks like you have acquired more of these chemical modifications.
And what about some specific changes, can you tell what genes have been changed? Sure.
As an example we could focus in on one chromosome, so let's take chromosome four, for example.
The changes that have occurred only in you, Alex, are in red and the changes that have occurred in Chris are shown here in blue.
So the, the blue bar is much, much bigger in me from 2008 to 2009, whereas Xand has stayed pretty much the same.
That's correct.
So I'm much more chemically modified in that gene than he is? That's right.
Although it's the same gene we've modified it differently? Yeah.
And that means that it's likely to be expressed differently, the gene will be turned turn or turned off? Yes.
And do we know what those two genes do then? We do.
So we've had a quick look at the function of these genes and they seem to be involved in metabolism.
That's interesting because there seems to be a metabolic difference between us at the moment, he's much heavier and we've had a metabolically different year, haven't we? I've had a very active year, I've gone to Africa and gone to the Arctic and been very active, busy job, cycling to work, and as far as I can tell you've done nothing but eat all year and allegedlyand allegedly did read some books.
And work.
Yeah.
Right.
This is the final piece of the puzzle.
Although Chris and Xand are genetically identical, their lives have continually affected the way their bodies work, these changes have, in turn, modified the way their genes are expressed.
Thanks to the different experiences they've had in their lives, Chris and Xand are now epi-genetically unique.
Epi-genetics is so revolutionary that it's changing the way that scientists like Professor David Leslie are thinking about some of the world's most widespread and debilitating diseases.
I started off as a geneticist but, because I've been studying twins, I've now become a non-geneticist, because I know it's not the genes that give you these diseases, it's the environment that gives you the diseases in interaction with the genes.
So it's that interaction which is important, and that's why epi-genetics is so important, because it's a fingerprint of that interaction.
One such disease is Type 1 diabetes, it affects 20 million people worldwide.
Sasha Jacombs has been living with diabetes since she was five years old.
If her blood sugar drops too low, she has fits.
I've had several fits when I've gone so low I just like start like She screams, she doesn't remember it but they're the scariest thing ever.
No.
I zone out and I won't know anything and then I'll wake up and everyone's pouring sugar on me and I'm like "What?".
The most scariest thing in my life seeing Sasha with a fit, cos she just screams and flails and it's horrible, and I never thought she was gonna come out of it.
For Sasha and Becky's parents, Jackie and Terry, it's the nights that are particularly hard.
For the last ten years we, one of us has had to get up in the night, so she normally gets checked at probably sometime between 11 and 12, and then one or other of us will get up at half past two in the morning roughly, to check, and then I usually get up at half past six each morning to check, so, and that's that's normal life now.
Sasha's identical twin sister, Becky, doesn't suffer from diabetes but the disease still affects her.
Because of Sasha's diabetes, I probably worry about her more than she's ever gonna worry about me, and I do think about her probably more than most people think about another sibling.
So I still have quite a high chance of developing it myself, but I probably tend not to think about that because actually that's kind of depressing.
Professor Leslie has collected DNA samples from twins where one has diabetes and the other doesn't to look for epi-genetic markers.
We've been able to identify a series of genes which have these epi-genetic markers, which are associated with the disease in the diabetic twin, but are not found in the non-diabetic twin.
These epi-genetic markers could help diagnose and treat diabetes much earlier.
We're developing now our various vaccination programmes, which have been successful in limiting the disease process in people with the disease and obviously would be probably more successful if we were able to treat people before they developed the actual clinical diabetes.
The latest medical advances achieved through epi-genetics do go way beyond vaccination and diagnosis.
Now epi-genetic treatments for life-threatening illnesses are reaching the final stages of clinical trials.
One epi-genetic therapy offers new hope for patients like Rajesh, diagnosed with MDS, an early form of adult leukaemia.
We were just shocked with the diagnosis, it was like the world come standstill because if this condition got worse going to leukaemia and then you're looking at what - a life expectancy of 18 months.
All the time I was in bed because I was not feeling 100% at all, I was not - I just didn't want to do do anything, just my body won't let me do anything.
This revolutionary new treatment is being trialled at King's College Hospital in London.
Epi-genetic therapy is where you give medication that modifies the genes which are structurally normal but those genes are not properly expressed.
So the drug reprogrammes these cells so that they are able to produce certain proteins normally which then tell the cell not to divide as a leukaemic cell again.
After a few months' treatment, Rajesh now has a normal haemoglobin level.
The next stage will be to do a bone marrow transplant, so that he's cured of his disease and that's what we are planning to do.
But this particular drug and this form of therapy definitely allowed us to give him the treatment without having any side effects, like any chemotherapy side effects.
Well, he looks so much better now, the little one keeps saying, "Mum, you've got a problem taking Daddy to the hospital, "there's nothing wrong with him, he's fine.
" And I just wish that everything comes back to normal, we can go back into a normal life.
Its a very exciting area because for the first time, we are looking at not quite killing the leukaemic cell but we are able to reprogramme the cells so that they can go to functionally competent cells.
The main area where these drugs are being looked at and will probably have a very important role to play, will be cancer.
Epi-genetics is at the cutting edge of modern medicine.
It's one of the most exciting new areas of science, helping us to understand how diseases are caused and how they might be treated, and thanks to twins, we're gaining ever greater understanding of what makes us alike, what makes us different and what makes us who we are.
They've helped to reveal that some of the most profound influences on us occur between conception and birth and that the genes we inherit from our parents don't work on their own but are controlled by epi-genetics.
Epi-genetics may even influence the genes that control normal development in the womb, turning some cells into brain cells, bone or skin and occasionally triggering random and unexpected differences that could set identical twins on different paths before they're even born.
Colin and Hermie's twin boys have been in the womb for 36 weeks, long enough for significant differences to develop.
Now they're going to be delivered by Caesarean section.
Yeah? Right.
Oh, no, I'm fine.
This is the right twin, I think.
Can I havethank you very much.
Hello.
Hello, we've got, ooh, that's the first twin, that's the right one.
OK? There we go.
Wonderful, that's the second twin.
Just hand him a minute.
Thank you.
Congratulations, well done.
I just can't believe one minute they were inside and then now, you know, they're just here.
They're so tiny and perfect.
Although their shared DNA will make these twin boys incredibly similar in so many ways, their destinies are not written in their genes.
By living different lives, they will influence which of their genes are turned on or off, shaping the people they become.
As nature's clones, twins will continue to enlighten us, and perhaps by the time babies Finn and Max have grown up, we'll understand even more clearly what really makes us who we are.