Jeff Craig, Jeff, Bruno Riverside discussed on Science Friction
Prove that. I'm Elizabeth coalesce and I am an identical twin. I'm also a mirror twin. And that's what we're talking about today on science fiction with Jeff Craig, he's a Professor of epigenetics that they can university and he's a twin researcher. And Jeff tells me that the rate of identical twinning sits at around one in 250 births. And it's more or less consistent around the world. For fraternal twins, that rate varies widely. From one in 200 births right up to one in every 20 births in some parts of the world. And in recent years, researchers have learned a huge amount about the biological origins of fraternal twins. This has been, I think some of the more exciting research that's come through about 5 years ago. There was some research came from genetic studies comparing families with higher proportions of fraternal twins. And what came out of that are genes associated with fertility? And fertility hormones. So what it comes down to is that some women are more likely to produce two eggs at the same time. Instead of one egg every month, not all the time, but more than average. And there's a number of factors that can influence this and some even think that diet in some African countries like, you know, it's been proposed that high diet in yams in South African countries may be an environmental component that may increase fertility and ovulating two eggs. And so there's been some evidence to back that up that yes fraternal twins often run in families for that reason. But whether identical twinning is a heritable trait. That's proving a much harder question to answer. Though it's not stopping some from trying. Well, we first off, I think we know that it is very rare to find clusters of identical twins and by clusters, I mean extended families with at least say three to four pairs of identical tunes in the family, but really it is rare. And the genetics that we talking about probably is not something that occurs very commonly. And Jeff, I hear that there is a twin hunter. Now, he's interested in whether there are unique families around the world where this is happening. What does he get up to? Yes, the researcher's name is Bruno riverside. He's a developmental biologist. He tries to understand what happens very early on when we develop. He looks at animal studies and he also looks for remote communities, which have a much higher incidence of identical twins. Which would imply that that particular community have some genes that code for something that affects early development and causes splitting. And so he's still on that long quest and I think he's found two remote communities. Well, he does this goes in. I guess permission to collect cheeks swabs, and then reads sequences to genome and looks very carefully to see what the differences are between these communities and everyone else. And he's got clues so far but it really hasn't come out and said, yes, I found I found the gene. There's never ever one gene for anything, but I found a gene that contributes to twinning. So it's ongoing research, but I think I love the idea of having the license licensed for sure the world looking for remote communities. I've always wanted an excuse to do that. Professional twin hunter. Yeah, I like it. Yeah. He's always on the lookout. He said, you know, that criteria of at least three or four pairs of identical twins he said you'll fly out and take 6 swabs if he finds more families like that. So far, I haven't found any two twins research Australia. But you never know there may be out there. Another statement that I'd heard all my life as an identical twin was that my sister and I were a complete DNA match. So I asked Jeff about this and he tells me that our understanding of that too has changed in recent years. Research into genetic difference in twins has been we're being drip fed that the last ten years in the genetic era. But only when we've been able to sequence all 3 billion base pairs of our genetics as the result being coming through. And a big study last year found that the average identical twin pair, it's actually different in about probably 15 locations in the genome. That's out of 3 billion, you say? Yeah, out of 3 billion. It's not a lot. And that can be anywhere between zero differences and a few hundred differences. Now the big question is where those are much of our genome is either Joan Carr antiques depending on your academic point of view. There's very little that actually codes for anything. However, it would be great for such a study to focus on identical twins and say, well, where are these 15 genetic differences? Are there any examples where researchers had found that it did code for something and led researchers in an interesting direction? Yeah, I think in that case, there was a single genetic change that was in a coding region, important region of the gene, and it was in a gene that was known to cause epilepsy in singleton. So yes, in this case, a one genetic mistake in a known epilepsy gene was shown to cause epilepsy in one twin of a pair. But despite all these recent discoveries, there remains a core mystery at the center of twin research that continues to confound science. It's probably the most fundamental question when it comes to identical twins. Just how and why? Does a fertilized egg split into? I find the very idea of the splitting process to be quite miraculous. Yes, and it is the only it's so miraculous that the only other mammal to have identical twins is the 9 banded armadillo. They actually have identical quads and octuplets. Nobody knows why we have this affiliation with armadillo with ambiguities, but it is actually quite rare in the mammalian world. But no one's ever seen a human twin split. But then late last year, a team in the Netherlands made an incredible discovery about identical twins. It had been a desert of research for many years, and just any clue to the formation of high technical twins was breakthrough. It was an international study. Didn't look at genetics, but they looked at epigenetics, basically these other dimmer switches that act on top of the genes to turn them off and on or up and down. And they compared epigenetics from about 3000 twins, some of which were identical others fraternal and they also included some singleton in there. So they were saying, what is this molecular event that makes identical twins special? The researchers hypothesized that the splitting event, which leads to identical twins. It could be embedded in the body's cellular memory. Every time a cell divides, the splitting would be remembered. So to speak. Not in the DNA sequence itself, but is a series of epigenetic chemical markers along the genome..