Influence of Genetic and Environmental Factors on the Development of Behaviors – Biological Bases of Behavior (PSY, BIO)

00:00 Okay. Let’s take a look at the influence of genetic and environmental factors and how that shapes the development of our behavior.

00:06 So we know that behavior is shaped by individual experiences and our social experiences and development of one’s behavior is shaped by a couple of key factors.

00:15 One, we’ve already mentioned, is biology.

00:18 So what are the genes? The genetic information passed on to you is going to be a huge driver of your behavior.

00:25 The second is actually prenatal development, so before you’re even coming out to the world to say hello, while you’re in your mother’s womb the environment there, the conditions there, the conditions that impact your development will have a huge role, and in physiology, as well.

00:41 Now, let’s talk about the brain.

00:43 Psychology, psychologically speaking, the gene environment interactions, prior experiences, beliefs, feelings, culture -- sorry, not culture. These things will really impact your psychology.

00:54 What is the psychological support that you have? What’s the support network? These things will all really play a huge role in relation to our third point of societal and cultural factors.

01:03 Do you have family? Do you have friends, the people you can get help from? What are the cultural norms around behavior? That will really have a huge impact on how you interact with the world around you.

01:13 So all these different things can really, really impact and change the development of someone’s behavior.

01:20 Now, let’s take a look at the role of genes in behavior.

01:23 So molecular biology is the study of molecular underpinnings of the process of replication, transcription, translation, and cell function.

01:31 So in your genetics module that you’re going to have to do prepping for the MCAT, you’re going to go through all of this process.

01:37 So what I want you to understand is there is a process where DNA ultimately gets converted into proteins, and throughout that process of protein expression, that can have a huge impact on actual behavior.

01:50 So now we’re linking biology, good old biology to actual psychological changes and output in societal behavior.

01:57 So Central Dogma of molecular biology is an explanation of the flow of genetic information within a biological system.

02:04 So we say that DNA makes RNA, and RNA makes protein, and this makes -- sorry, and the protein expression can impact behavior.

02:16 So it’s kind of a neat idea.

02:18 So DNA, which is encoded in you, through different processes makes RNA, which makes protein, and levels of protein expression will affect your ultimate behavior.

02:27 So when we’re causing a change in behavior, we’re actually getting right down to the level of protein expression, okay? So that’s a really cool way to look at it.

02:37 So we’re going to look at sort of regulatory genes and behavior.

02:40 So we have DNA through the process of replication, and we’re not going to get into a whole genetics discussion, but we go on to transcribe RNA, and then we go on to create protein.

02:52 Now, different levels of protein expression like I say will affect behavior.

02:57 Now how is protein expression controlled? Well, it all goes back down to regulatory genes.

03:04 So the human genome is made up of 23 chromosomes.

03:08 So this has all been mapped out.

03:09 So for the human genome we have mapped out all the different chromosomes and what it is that they do.

03:15 So, a couple of really interesting things.

03:17 Protein-coding sequences account for only 1.5% of the entire genome.

03:22 So out of the whole genome, only a very, very small fraction is really influencing protein-coding, okay? So vast quantities of non-coding DNA within the genome are associated with biochemical activities including gene regulation, so the bulk of the genes, a bulk of the DNA is doing something else.

03:40 A gene regulation can modulate the expression of a protein versus direct protein-coding.

03:46 So what we’re saying is the bulk of protein is normally coded by that 1.5%, and if you go on and activate and inactivate and modulate or modify the other genes, that can go on to impact protein.

04:00 So you’re using sort of an indirect means to influence protein.

04:03 So the direct effects of these changes and changes in protein expression will impact behavior.

04:12 So epigenetics is the study trait variation caused by external environmental factors that switch genes on and off.

04:18 So this is a burgeoning area of study now because people are really, really interested in understanding well, what is actually impacting my behavior? What in the environment, what around me is going to activate or inactivate certain genes? So study of how cells read DNA instead of being caused by changes in DNA sequence, okay? So processes like methylation or histone modification alter how genes are expressed without changing the DNA sequence.

04:42 So we’re not actually changing the sequence of your DNA, we’re just changing sort of the on and off.

04:48 So you should be familiar with the fact that methylation or histone modification refers to the fact we’re turning gene expression, okay? So that’s the on and off versus actually changing the DNA sequence, okay? So we got some figures and some analogies, this might help you.

05:04 So if a gene is switched on, we have active chromatin, and that means it’s open.

05:09 And unmethylated cytosines, and we’ll have a diagram, those are the ones with circles, they’re still there, and we have acetylated histones.

05:17 Now on the off side, it’s silent.

05:20 We have condensed chromatin, the methylated cytosines, which are red circles, and we have a deacetylated histones, that would be the off switch, okay? So here in this diagram you can see the little circles represent the histones and the methylation.

05:34 So on the top transcription is possible, and so we have normal DNA production and protein production with RNA transcription, and on the bottom one we can see that transcription can be impeded and now you actually can’t just transcribe, you can’t cause the protein expression.

05:51 So one is an on, and one is an off.

05:53 And so based on the environmental influence, you can be in one of these states, in an on state if you’re normally on a resting state, or it might be the opposite, you might be turning an on gene off and, again, that will impact the level of protein expression.