JEN, Jeff Craig, Deakin University School Of Medicine discussed on Science Friction
Unique. We were 6 when we first attended an in person clinic for the twin study. We traveled to a grand old medical building on the fringes of Melbourne's CBD. I remember huge staircase and the polished floors, and being told that we were going to have a cheek swab taken. Oh, yes, I remember being very scared that the cheeks what was gonna hurt and then the anti climax when it was a cheeks woven. It was totally fine. It was like vaguely uncomfortable for a millisecond. Jen and I were part of a study being run by the university of Adelaide, looking at the jeans, teeth, and faces of Australian twins. The shake swap was taken for a zygosity test to confirm whether we were fraternal or identical. For total twins, the result of two eggs being fertilized by two separate sperm. For tonal twins share about the same amount of DNA a single born siblings, or singletons, as they're known in the twin research world. Identical tweens are the result of a single fertilized egg, but splits to create two embryos, so their genetic profile is a much closer match. Jen and I were never dressed the same, and we were always placed in separate classes at school, but beside our closest family and friends, just about everyone else struggled to tell us apart. And a few months after that cheek swap around the time we turned 7. The results came here. Despite what our mother had been told when we were born. Jen and I were identical. As a gossip story, turns out it's actually quite a common one among tweens. It's something researcher Jeff Craig first encountered about ten years ago at a twins festival in Melbourne. Yes, you heard me. That's absolutely a thing. And at this festival, Japanese team were offering free zygosity tests. We put an advertisement just one week before the festival on the twins research Australia website. We think, oh, and that got a handful. And we opened the doors after we set up a culture race course. And there was like a tsunami of parents and they're pushes just queuing up a big air to find out the truth. Jeff Craig is a Professor of epigenetics and cell biology at deakin university school of medicine. He's also the deputy director of twins research Australia. And Jeff was surprised at what they discovered next. Up to one third of those twins were either misinformed or just simply didn't know about their own identity whether identical African. So that's quite a lot. So not alone in being late to find that out. Yes, there's many many twins. I think our oldest twins who found out were in their 80s. Oh wow. And so we realized that there were myths going around such as if twins each had their own placenta, there must be fraternal, and we now know that it's not necessarily that way. One third of identical twins also have their own placenta. The remaining two thirds share a placenta. And I guess one of the other myths was that identical twins must be identical in every way. Including personalities teeth, et cetera, and that's not the case identical twins can be physically and behaviorally different as well. I think those were the main two myths. The study of twins has a long and at times checkered history. So Francis galton a distant cousin of Darwin was among the first to recognize the research potential of twins. A prominent figure of Victorian science, his work in the late 19th century used twins to explore the influences of heredity and environment, paving the way for the debate over nature and nurture. Into the genetic era, researchers continued to work with twins. As a kind of naturally occurring experiment. The first kind of research was asking whether a condition was more influenced by genes or environment. And even though now, we know it's always genes and environment. The knowledge genetics and knowledge of environment has been important. For example, it was suspected that smoking increased the risk of bone fracture. Researchers knew there were many things that could influence the risk of bone fracture. So in an earlier Australian twin study, they started recruiting identical twin pairs, where over a period of years, one of the twins smoked, and the other didn't. And so that particular type of model same genetics for definite environment was very informative in this case. It said there was a causative link between smoking and bone density and therefore they could conclude that smoking lower bone density is more likely to lead to osteoporosis and fractures. Because they took that genetic component away and looked only at that environment. Even before Jen and I had received our zygosity test result. We'd been contributing to our twin study in another way. By collecting our baby teeth, we were each given a small jar, clear plastic with a yellow lead, the kind used to take pathology samples. And inside was a little slip of paper, showing two neat semicircles of teeth, sketched in a line drawing. And do you remember collecting our teeth for this study? I do remember evening the taste and now I look back on it because you keep your teeth for the tooth fairy anyway. I think I just thought that this strange little container with the yellow lid was was just an extension. It was like a little tooth vault. Any time either of us lost a tooth, we were asked to store it in a little tooth Volt, and to write the date that it had fallen out next to the corresponding tooth on the diagram. By the way, we asked the two theory to please respect science and leave the coins, but also leave the teeth. We did this over a series of years, collecting, dating, storing teeth away. And soon, a pattern emerged. Not long before finding out, I can remember, you know, losing yet another baby tooth. And us losing those teeth within a day of each other. And they're happening on opposite sides of our mouth. There was these kind of breadcrumbs that we are linked in some quite extraordinary way. And this kept happening. Our teeth following the same eerie pattern over and again. Jen would lose a tooth on the right side of her mouth, and somewhere between a day and two weeks later, I would lose the same tooth, but on the left side of my mouth. And as we started learning to write in developing our fine motor skills, other signals became clear. Jen was predominantly left handed, where I almost always worked on the right. And somewhere in those data collecting years, we would hold this likely had meaning. Jen and I were mirror twins. When we look in the mirror and a single tip, well, we, when I look at the mirror, we see ourselves. We can identify that's my left side. That's the mirror of it. Well, with twins, it's like the mirror is not there in twins are looking at each other. And there's a lot of physical features such as birthmarks and hair walls, et cetera. And even internally, there's been some with the organ positions, et cetera. So it's kind of an experiment for twins to do if they haven't done that to see how similar are on the opposite sides. Science doesn't know who very much about Mira twins. Identifying them is actually quite subjective. There's no official diagnostic criteria. And for this reason, Miro twins have often been seen as a messy group in terms of research. Because myriad traits aren't consistent across twin peers, reproducible research is difficult, ordering on the impossible. We really don't know much about it at all. We know it happens in around one in four identical twins. And everything else is guesswork, we assume it's because when they identical twins split is maybe just after the time where the genes that determine left and right start being switched on, but we.