DNA and Behavioral Genetics - Robert Plomin

behavior genetics has been going on for over a century the modern era began in 1960 with a book called behavioral genetics but people have been interested in nature and nurture for recorded history animal breeders knew that you could breed for behavior and most animal breeding involves behavior as much as it does biology you know you think of all the dog breeds are mostly bred for functional behavior for very specific things like pointers point and scent hounds smell and it's hard to get another breed to do that you try to get a you know a collie to point you know they won't point try to get a pointer to round up sheep you know so for a long time we've known that genetics is important but psychology rejected it for humans you know fair enough but after a century of research things have changed dramatically most psychologists now accept an important role of inherited DNA differences so much so that it's no longer interesting to say oh here's another trait another measure let's see if it's heritable you can save time by just saying yeah it is it's going to be we've got to ask more interesting questions and the big one is can we find some of the genes and that's been a revolution and it's just now reaching a point where we're identifying some of the genes to be able to make individual predictions and this isn't just psychology this is all of the life sciences they've all come to this position everything's heritable let's find some of the genes because if you can find the genes you can understand pathways between DNA RNA metabolism proteins brains and behavior and so that's the original goal is to find some of the genes so you can really understand the mechanisms between genes brain and behavior but what we've learned from these new strategies that just came out really in the last 10 years or so called genome-wide Association studies where you have a little chip the size of a postage stamp and it allows you to genotype hundreds of thousands of DNA markers throughout the genome which are the 23 pairs of chromosomes 3 billion base pairs of DNA you can tag it throughout the genome so genome-wide Association study is an a theoretical approach to find the genes for heritable traits the biggest thing that's come out of that is that the biggest effects are much smaller than anyone ever thought so the biggest effect we know of for say a complex trait is one gene called FTO which predicts body weight you know how heavy you are corrected for height called body mass index it's called well that accounts for about 1% of the variance in weight but that's by far the biggest effect that's been found and 1% translates to this you know it's a it's a stretch of DNA that has two forms a and T it's called if you're a a you're three pounds lighter than the average if you're 80 you're average if you're TT you have three pounds greater so it's like a six pound difference that's what 1% of the variance is that's the biggest effect the average effect sizes are less than 0.01 it's really like 0.1% 0.1% of the variance incredibly tiny effect that's the biggest effects and what we're guessing now is that the smallest effects are very much smaller so if we're talking about here the biggest effects the smallest effects account for most of the heritability so what that means is we're not looking for the gene or even a handful of genes we're now talking about thousands tens of thousands of genes that we put together in what we call a polygenic score multiple gene score and we're now beginning to use those to predict genetic propensities in a population so for height we can now explain with DNA alone 20% of the variance with weight about 15 percent of the variance so that means then the difference the thing here is you could predict that at birth about an individual and in psychology and psychiatry we're nowhere near that with schizophrenia people say they can explain about 10% of the genetic risk with DNA alone with these they're called chips these little postage size stamp slides in a way that you use to genotype DNA that you just get from saliva so to detect these small effects you need huge samples so the sample sizes are in the hundreds of thousands so you need a hundreds of thousands of people who have been genotyped on hundreds of thousands of snips we call them single nucleotide polymorphisms it's just a DNA variant and that's what we need to be able to detect these tiny effects but when we get up to those sample sizes we are detecting those effects so for behavioral traits that I study like intelligence six months ago we were able to explain 1% of the variance we can now explain 5% of the variance with educational achievement though we can explain 10% of the variance so that means you take these tests in in England we have these tests called GCSE which all children at the age of 16 at the end of compulsory schooling have to take national exams we can explain 10% of the variance on that now that's we just got started and we can explain 10% of the variance it's about 60% heritable so we've got a long way to go but with 10% what it means is if you take the top fifth in terms of these genetics scores we call polygenic scores the kids who are in the top fifth are 65% likely to go to university the kids in the bottom fifth are 35% likely to go so even with only explaining 10% of the variance that's a pretty big difference in terms of predicting at the high and low extremes so I'm really into this because I want to be able to predict genetic strengths and weaknesses at the individual level that's not to say it's not like family risk if you had a first-degree relatives alcoholic you have a 5 for greater risk of being alcoholic but so does your brother because it's just the family risk that doesn't work for people because there's big genetic differences within a family you and your brother can be genetically quite different but with DNA you're able to make up specific risks we could say you're at risk for becoming alcoholic your brother is not and what that would mean that is if you guys drink the same amount of alcohol you're gonna become alcoholic your brother won't be this is just you know in terms of the genetic prediction it's not all genetic but it's saying that genetics can make a pretty good prediction about some of these things and when we do that it'll change research because it's so cheap to do this now these chips I talked about when I first did it they cost about three thousand pounds they're now 40 pounds it's cheaper than much of the stuff we do in psychological research you need big samples to find these polygenic scores but once you find them you can use them in studies in small studies like in neuroimaging studies or in psychological studies so it's going to change the face of research because we're going to get DNA on everyone Francis Collins who's the director of the National Institutes of Health and was the director of the human genome project he says that within a few years all newborns will not just be given will not just be genotyped on a chip their whole DNA sequence of 3 billion base pairs will be sequence and you can put it on a little memory stick and once you've done that that's the end of genotyping in collecting DNA you don't need DNA anymore everyone will have all their DNA bases on this memory stick and then we'll use that then to create these polygenic scores to make genetic predictions of risk and for me especially what I'm interested in is reading disability and reading ability are highly heritable what we do now is we wait the kids get to school they fail at reading and then we try to do something to fix it you could predict which kids are likely to be at risk and we already know that almost all kids who are reading disabled have language problems earlier you can't do reading interventions in three-year-olds because they can't read but you can do language interventions because there's very good language programs but an important point is most successful interventions are expensive and intensive so you can't do them with everybody but if you could identify the kids who will be at risk for reading you could intervene with language and it wouldn't hurt them it's not like giving them a drug or something it's only good you know to have people helping you with your language and then when they go on to school they'll be less likely to have a reading problem so all of science medicine now is focused on predicting and preventing problems waiting rather than waiting until the problems occur and then trying to fix them so this is beginning to happen now people are doing it on their own 23andme is this company that will do this for you this genotyping for about a hundred bucks for example so lots of people are doing it and they're beginning to do it for their children the reason I think it's important to get this message out now before it really hits the ground you know explaining 10% of the variance is a lot you know if you want to predict like school achievement what's what what would you use to predict that nothing else will get near this ten percent ten percent is a lot but we've just begun people don't even know about this yet but when they do I think they will begin to take genetics seriously in education right now they totally ignore genetics and I think there are some very good things they're good discussions that ought to begin now before this really becomes reality even though it's getting close to reality already and I think you know a lot of people say how terrible this is imagine you're gonna predict which kids have reading problems I think that's good now there's a lot of doom mongers and say oh you label kids well kids get labeled already you know there are problems we got to discuss those problems but I'm a cheerleader for this I think we can do a lot of good at predicting and preventing problems from occurring but even right now before we find the genes we got to start realizing that genetics is very important it accounts for far more variance than anything else and what that does is it makes us recognize that people differ genetically it isn't all due to learning or willpower or personality it's you know DNA differences from early in life and when we recognize those differences we might respect them more so I think one message that comes out of genetics is tolerance like right here in the in the UK weight is a major issue you know the obesity epidemic and people are seriously saying that overweight people should be made to pay for the disorders that occur they oughtta have to pay for their National Health Service because it's their fault they're there fact why don't they just know his way but if you recognize the genetics seventy percent of the differences are due to genetics you realize it doesn't mean you can't lose weight if you stop eating you lose weight but if you're thin you don't recognize how difficult it is for someone with a genetic propensity to put on weight and have great difficulty losing it you know it's just a lot harder and with learn of reading disability doesn't mean genetics means you're not gonna teach kids to read it just means some kids are gonna find it much more difficult and we need to recognize that instead of say in the case of education blaming the schools blaming the terrans parents blaming the kids and and with obesity blaming you for being a slob you know just get a grip have some willpower here lose weight and you know so I think if we recognize it's it's easier for some people to say that than other people we might become more tolerant but at least what it will do is have us realize people are different and that suggests that medicine you know we talked about precision medicine that's basically genetics not prescribing drugs one size fits all not having a National Curriculum one size fits all but recognizing that people differ genetically and they need interventions that are personalized to them so I think that's one of the big messages that come out of this even before we identify the specific genes that are involved you

Channel: Serious Science

Views: 52,835

Keywords: science, lecture, Serious Science, genetics, educational achievement, intelligence, genetics of intelligence, behavioral genetics, neuroscience

Id: BYGUjIlq5yA

Length: 13min 14sec (794 seconds)

Published: Tue Dec 13 2016