What identical twins separated at birth teach us about genetics - BBC REEL

[Music] my name is dr nancy siegel i'm a psychology professor at california state university fullerton what got me into twin research initially is that i am a fraternal twin and always fascinated with the similarities and differences mostly differences that my sister and i have and i used to wonder as a child how this could be if we had the same parents and same environments and when i began to study psychology at the high school and graduate school level i learned about genetics and how we all come into the world with predispositions of our own and that explained while my sister and i were so very very different well i spent many years at the minnesota studied twins raised apart looking at identical and fraternal twins who've been separated at birth it's very important to include the fraternals because they're the natural control group and let's think about the differences between those twins before looking at the insights identical twins share all their genes having split from a single fertilized egg within the first two weeks after conception fraternal twins share half the genes on average they result when a woman releases two eggs at the same time and they're fertilized by two separate sperm so they have 50 of their genes in common on average like ordinary siblings comparing resemblance in identical twins to fraternal twins gives us a handle on whether or not genetics has an effect it would if identical twins are more alike than fraternals and they invariably are studying twins gives us enormous insights into how we come to be the way that we are twin studies are a natural model we're looking at genetic and environmental influences on behavior and what we are finding is that many more behaviors than we ever would have thought do have a genetic component to them genetics is not everything but it does explain a great deal of why we differ one person to another well let's start with looking at genetic influences on physical traits we find that height and weight have substantial genetic components we find that general intelligence has a substantial genetic component a little bit less than in some of the physical traits like height and weight and brain waves but nevertheless a substantial genetic component as does special mental abilities and then we drop down a bit when we get to job satisfaction probably the most surprising findings in the last 20 years or so have been that things like religiosity how much you invest in religious activities and interests and political attitudes and social attitudes have a genetic component to them it's very important to appreciate that genes do not work in deterministic ways they work in probabilistic ways they predispose but they do not provide the final word genes change in expression just because you have a gene doesn't mean it will always be expressed it takes a certain environment to bring that out we all have genes that will be expressed given a particular environment now with identical twins they have the same dna but sometimes gene expression can occur in one twin and not the other and this can create differences between them and these environmental differences that trigger different gene expression might even start in the womb the beauty of identical twins raised apart is that they share only their genes and not their environments so any resemblance between them is tied to their common genes we find some amazing similarities and identical twins raised apart many more than we ever would have anticipated not just in the more traditional areas like intelligence personality physical features like height and weight but in some more unusual habits such as a pair of twins who both used to scatter love letters around the house to their wives and both bit their nails down to the nub and both explain their same mixed headache syndrome in exactly the same way as if someone is beating on their head with a hammer these are very challenging and you can ask yourself are they due to this random chance my answer to that is no they're not and the rarer they are the more i believe it's somehow tied to their genes and the way the genes interact with their environments to produce these kinds of unusual similarities i think that the people who find it challenging or even disturbing are those who don't fully understand the process they think that genes work in deterministic ways when in fact they work in probabilistic ways and so it doesn't mean that we're set in stone we can't change it means that we can change we can alter environments to make behavioral expression different we can work to prevent disease or to mitigate it but we can't all be the same [Music] you

Channel: BBC Global

Views: 2,492,582

Keywords: bbc, bbcreel, bbcnews, factual, features, twins, nancy segal, nature, nurture

Id: JMlJcOSRX-8

Length: 5min 40sec (340 seconds)

Published: Wed Feb 16 2022