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Behavioral Genetics – Biological Bases of Behavior (PSY, BIO)

by Tarry Ahuja, MD
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    00:01 Now, let’s get into behavioral genetics.

    00:06 Genetics, hereditary genes, behavior, temperament, these are all things that have been coming up in lot of our modules.

    00:14 And right now we’re going to break this down into the main components that make up behavioral genetics.

    00:19 So first we’ll get in some basic nomenclature, genotype.

    00:23 So genotype of an organism is the inherited map it contains within its genetic code.

    00:28 So that’s the genetic information.

    00:30 The phenotype is the observable characteristic and traits of that organism.

    00:34 So having blue eyes or brown hair or a certain color of skin, that would be the expressed phenotype, but what’s mediating that and what’s controlling that and what’s causing that to be expressed would be the genetic information or that person’s genotype.

    00:48 Behavioral genetics examines how genotype and the environment affect our expressed phenotype.

    00:54 So just because you’re wired to have a certain genetic trait, so genetically, on the blueprint it says you should have this, it doesn’t necessarily mean you’re going to actually express that, and that’s because of the impact that the environment can have.

    01:09 So heredity is the passing of traits from the parents to the children, so eye color, hair color, that’s passed on.

    01:17 We’ve also talked about things like certain behaviors or certain disorders or being prone to certain disorders, being genetically predisposed.

    01:24 That means you have the genetic -- you have the genotype to potentially, say, get depression because we’ve shown a hereditary linkage between parents and children when we’re talking about this disease, and that’s through the passing of this genetic information.

    01:43 Traits or attributes can include things like eye color, hair color, shape of face, which we’ve discussed, and individual traits are encoded in this DNA.

    01:51 Now, if we’re looking at the actual process, and again, we don’t need to memorize all of these various steps, but what we’re saying is we have the genetic information found in chromosomes and that goes on to then go through the process of transcription and expression and we get expressed behaviors, and this is all linked back to the actual DNA.

    02:12 So we can go in and look at specific strands of DNA, understand the sequence, and that gives you a good a map of exactly what controls what.

    02:23 So we’ll look at that in just a sec.

    02:25 So genes and environment work together to influence our state, active versus inactive.

    02:30 So a gene, just because it’s there it doesn’t mean that it’s actually going to express itself, it needs to be activated, or it can be inactivated.

    02:38 So we know that the environment can actually have a huge role in activating and inactivating genes.

    02:45 So we say the environment can mediate level of chronic stress and can activate or inactivate specific genes.

    02:52 So let’s use an example, you’re a modestly healthy person, life is good, you have no disorders, everything is great, and all of a sudden you start studying for the MCAT, it’s kind of stressful, you get in medical school, kind of stressful, you become a well-renowned surgeon, extremely stressful.

    03:08 Being in the stressful environment will actually modulate and change expression of specific genes.

    03:14 And we’ve shown that this chronic exposure to stress will then go on to activate or inactivate these genes depending on what it is that they do and depending on what effect those environmental stressors are having one you, and this can then go on to lead to behavioral or phenotypic changes.

    03:31 So great example of how the environment is impacting expression of your genes which goes on to change the expression of a behavior or your phenotype.

    03:42 Now, temperament is something that’s unique and it’s sort of how we express ourselves.

    03:48 It refers to the emotional excitability and aspects of an individual’s personality.

    03:52 So you can have different types of temperament and you hear people say what’s their demeanor or what’s their temperament like, or that person has quite a temper, and that’s what they’re referring to.

    04:03 So now, is this something that you’re born with, is this something that you develop? It’s kind of a combination of both, but initially, there’s a large innate, innate or from within at birth portion and there’s some of it that’s learned, but your basic temperament typically comes from innate behaviors or it’s innately set.

    04:23 So temperament also focuses on behavioral profiles that are easily measurable and testable in early childhood.

    04:29 So as a child, I can say this baby has this type of temperament.

    04:34 And I think to keep it simple, what we’ve done is we’ve put it into two broad categories.

    04:39 So you can have two main types of babies.

    04:41 The first being an easy baby, and this is a baby that’s fairly relaxed, easygoing, likes to play a lot, smiles, it’s quite engaged.

    04:50 There are ones that have good eating and sleeping schedules There are ones that have good eating and sleeping schedules and those of you who have young children always pray, “Please let me have an easy baby and not have a baby that’s whining and crying all the time.” So this baby is one that you can put down anywhere, they’re happy.

    05:03 You can pass them to anybody, they’re happy.

    05:05 You can put them to bed at three, at six, at nine and it almost doesn’t matter.

    05:08 They’ll sleep any time, they’ll eat anything, they’ll eat quite easily.

    05:11 These are easy babies, the dream.

    05:13 Now, the opposite is a difficult baby, still cute, but sometimes you maybe want to strangle them a little bit, right? And they’re highly irritable, easily upset, always crying and whining, and I’m not talking about like a toddler, I’m talking about a newborn baby.

    05:29 You try to put them on a schedule, you try to have them sleep, feed, eat, and that’s very, very difficult.

    05:33 So, thus, the names easy baby, difficult baby.

    05:38 Now, let’s take a look at the adaptive roles of traits and behaviors and how these change.

    05:43 Okay, so we’re going to look at a range of two types of behaviors, innate and learned.

    05:47 So these are ones that you’re born with and these are ones that you learn over time.

    05:50 They’re more adaptive in nature.

    05:52 So in the innate ones you have ones that are genetically programmed behaviors, inherited or they’re intrinsic or stereotypic, inflexible; versus adaptive.

    06:02 These are ones that are not inherited, that are extrinsic, permutable.

    06:05 They can change, adaptable, progressive.

    06:08 So, some of the innate ones are things like reflex, and we talked about that knee jerk reflex, orientation is how you orient yourself automatically, something called fixed action pattern.

    06:20 So an example would be, say, I’m thinking animal kingdom, a frog trying to catch a fly or the praying mantis that is trying to attack its prey.

    06:30 Once it initiates that response, which usually involves a couple of movements, it really can’t stop that.

    06:37 It’s a fixed action pattern, it’s fixed, it’s going to go and do its thing, So once that frog has got its tongue out trying to catch a fly, that’s it, it’s gone, right? And same thing with the praying mantis.

    06:46 Once it’s going to do its strike to hit something, that’s it, it’s a go ahead movement.

    06:51 It’s not really thinking about it and you just follow through.

    06:54 As humans, we have, you know, a lot of similar things where there are movements or behaviors that we do where once they’re initiated, you kind of just you go through, you follow through.

    07:02 Now, in reality, we know that it’s never really just purely innate or just learned.

    07:08 We have a nice mix of a lot of what we do is actually complex.

    07:10 So it’s a combination of the both and it’s done to allow us to maintain a certain consistency.

    07:17 And so one of that consistencies we’re trying to maintain is something called homeostasis.

    07:21 It refers to the body’s drive to maintain a consistent internal state.

    07:25 So a certain temperature, a certain blood pressure, and you need to modify your behaviors in order to maintain that homeostasis.

    07:31 So, some of the behavior modification can be done through this combination of innate and learned behaviors.

    07:38 So, this modulation of behavior is called adaptation, and we do this adaptation to maintain our homeostasis.

    07:47 So there’s a range of observable behaviors based on these categories.

    07:52 Now, let’s take a look at how we figure out what impacts -- what a lot of things are happening, whether it’s behavior or whether it’s a certain medicine or if we’re looking at a certain trait and we want to look at what impact that’s having.

    08:07 One of the easiest ways we’ve been doing this over the years is looking at twin studies.

    08:12 So twin studies allow us to examine the relationship between heritability and environment.

    08:16 So two main factors that normally will drive a change or expression in the phenotype or behavior are -- well, did you get from your genes or is this impact of the environment? So we have two types of twins.

    08:28 Monozygotic or identical twins and they have essentially the exact same genotypes.

    08:33 So what we’re doing by looking at these individuals is that we’re removing heritability out of the equation because the idea is if they have the same genetic information, you know, if one was being inherited, it should be with the other.

    08:47 So now we can look at if it was expressed or not, and that expression was going to be more prominently due to environment because we’ve removed genetics out of the equation.

    08:56 And there’s dizygotic or fraternal twins and this is where they share roughly half of their DNA.

    09:01 So here, the linkage isn’t as direct, but it’s still better than or is comparable to the general population.

    09:09 So heritability estimates the variation in a trait that is due to genetic variability and is population dependent.

    09:16 Okay? So if you’re in the general population, you would have a certain level of expression versus if it was in your genes, you would have an elevated level of expression.

    09:27 So it’s also influenced by environment, so shared environment versus not-shared environment.

    09:31 So you can have two twins that are monozygotic, so identical twins, and you separate them by birth and they live separate lives across the globe with two different -- completely different environments -- two different families, schools, friends, everything.

    09:45 We will find that a lot of behaviors and certain traits will be identical even though they have completely different environments, but then will also have certain traits that are environmentally driven.

    09:55 So it’s a combination of both.

    09:57 So heritability does not pertain to an individual, but rather to how two individuals differ, and that’s a really important point.

    10:03 So, the heritability is not saying something specific about that young girl, but it is going to allow us to say something that’s different between her twin sister or her and a comparable that’s in the general population.

    10:19 So an example is IQ.

    10:21 So if we say, you know, she has a certain IQ, I’m not saying that the heritability is influencing her IQ, it’s influencing or it’s allowing us to better understand the difference in IQ.

    10:33 Okay? So it’s kind of an important point that you got to grasp.

    10:37 So let’s take a look at the role that the environment can play on genetics.

    10:44 So genetics can be influenced by both the predisposition and the environment, so we’ve mentioned that before.

    10:49 You’re born with you genes and that’s part of the equation, but the environment can influence expression of genes.

    10:56 So a good baby versus a difficult baby and the resultant downstream environmental effectors.

    11:00 This is a great example of genes and environment.

    11:04 So take a look at this scenario, you have two babies.

    11:09 We have the first baby, which is the good baby, and this baby is amazing.

    11:15 The baby sleeps great, eats great, you know, it can pee or poo on demand, perfect and incredible child, and as a result, how do you treat that child? You’re like, “Oh, you know, my little Timmy, he’s an angel.

    11:30 He sleeps great, he’s such a cutie pie, he never cries and everybody comes around to check our little Timmy and they’ll gather around little Timmy. Oh, he is so cute.

    11:38 Look at him smile and he smiled at me.

    11:40 And will he let me hold him? Oh my God, he will.

    11:42 I think he -- what a nice kid. He’s such a sweetheart, oh my God, oh my God.” This continues, and let’s just roll this out.

    11:48 As he continues to be a good baby, he becomes a good toddler, always eats his food, sleeps on time, doesn’t argue, doesn’t cry.

    11:55 He can be playing with other kids, plays well.

    11:57 All of a sudden, people continued around him to say his mom, his dad, visitors, family, friends, “What a great baby. He’s such an amazing baby.” Now all this positive reinforcement is creating a pretty positive environment around that child, versus our devil baby, the difficult baby who’s not eating, who’s not sleeping, who’s always crying, is very, very difficult to handle.

    12:20 You know, people come over and they’re like, “Oh, can I see little Timmy?” And Timmy starts wailing and kicking and screaming.

    12:25 They’re like, “Well, maybe I’ll just put him down and whatever,” and you kind of internally will have this perception that what a difficult baby and you know, you know little Timmy is always crying, and so they get negative feedback.

    12:36 So now two different babies, potentially the exact same, you know, parents and interactions, but how those interactions are played out and the result in environment around that child changes.

    12:48 Happy baby, good baby, positive environment; crying baby, devil baby, negative environment.

    12:54 So that feedback that that baby gets as they grow and develop will directly influence how they express their behavior.

    13:03 So it’s pretty cool that, you know, the environment that you create will really have a result and effect on the the ultimate behavior.

    13:12 So, reciprocal relationship in that environment can lead to genetic variation.

    13:16 So if we’re looking at a positive environment, we see a reinforcement of genetic expression, and if you see a negative environment, you might see a change in that genetic expression.


    About the Lecture

    The lecture Behavioral Genetics – Biological Bases of Behavior (PSY, BIO) by Tarry Ahuja, MD is from the course Individual Influences on Behavior. It contains the following chapters:

    • Genes, Temperament and Heredity (PSY, BIO)
    • Adaptive Role of Traits and Behaviors (PSY, BIO)
    • Interaction Between Heredity and Environmental Influences (PSY, BIO)

    Included Quiz Questions

    1. ...temperament.
    2. ...heredity.
    3. ...genotype.
    1. Inflexible sleep schedule
    2. Calmness
    3. Playful
    4. Predictable feeding schedule
    5. Gets along with strangers
    1. Adaptable
    2. Fixed action pattern
    3. Knee jerk reflex
    4. Stereotypic
    5. Fully developed
    1. Homeostasis
    2. Temperament
    3. Personality
    4. Behavior
    5. Neurotransmitter
    1. Food
    2. Parents
    3. Culture
    4. Non-shared environment
    5. Genetics

    Author of lecture Behavioral Genetics – Biological Bases of Behavior (PSY, BIO)

     Tarry Ahuja, MD

    Tarry Ahuja, MD


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