Source: Peas; Public Domain http://www.morguefile.com/archive/display/687589 Gregor Mendel; Public Domain http://en.wikipedia.org/wiki/File:Gregor_Mendel.png DNA; Public Domain http://commons.wikimedia.org/wiki/File:DNA_Double_Helix.png
Hello, class. So in today's lesson, we're going to be looking at some of the biological influences and dimensions of developmental psychology. Now remember, biology, when we're talking about psychology, is the internal physical and chemical processes that influence our mind and behaviors. And we're going to be looking at two major aspects of biology today, as well as looking at some of the historical perspective and figures behind it. So this is part biology, part history lesson.
The first thing we want to talk about is heredity, which is when the physical and psychological characteristics are passed on from a parent to their offspring. Another term for this is inheritance, so we'll be using both of those interchangeably. The important figure to remember in terms of heredity is Gregor Mendel. Mendel is who we consider to be the father of genetics. He was an Austrian scientist and a monk during the mid to late 1800s.
And while he was at his monastery in Austria, he was examining the inheritance of certain characteristics of pea plants. He was looking at how he could pass on these different characteristics from one parent plant to the offspring. And there were seven particular traits he was looking at, which each only had two forms. For example, a pea plant would have a flower that was either purple or white, had a stem that was either long or short, and seed shapes that were either round or kind of wrinkly.
So he noticed when he was breeding for certain types of characteristics in pea plants, certain ones showed up more than other ones. And he started to write down and record those. He noted two specific types of these characteristics.
There are two different aspects. One was what he referred to as the genotype, which is the genetic makeup, the sort of blueprint underlying these physical characteristics, as well as the phenotype, which is to say the observable characteristics. So a plant might have the phenotype for purple flower, a long stem, and a wrinkly seed. And there's a genotype behind each one of those characteristics that tells the plant to display those kinds of inheritance.
After Mendel made his observations and his discoveries, he wasn't actually recognized for these accomplishments during his lifetime. It wasn't until the early 1900s when people realized how greatly important these things were and they actively started to study heredity and tried to uncover what the mechanism was for passing this information along from parents to offspring, as Mendel discovered. And they didn't discover that mechanism until 1953, when John Watson and Francis Crick published an article called "The Molecular Structure of Nucleic Acids," a structure of deoxyribose nucleic acid, or what we call DNA, which we know now is the biologic basis for heredity and inheritance. It's the thing within our body, within our biology, that allows the information to be passed from a parent to an offspring.
Now with DNA, the important discovery that they found out was that the shape of the DNA was what we call a double helix. And that shape allowed it to function as the information center for the cells. It's kind of like a zipper, where you're able to pull it apart and have two halves, which can be copied and sent down to different cells and to the offspring.
The middle of the DNA contains different nucleotide bases, which are the information for our cells. There are four of them. There's adenine, which we denote as A; cytosine, C; guanine, which is G; and thymine, which is T. And these different types of nucleotides pair together, so A goes with T and C goes with G.
So what effect does heredity and does DNA have on psychology? Well, we have to think of behavior and mental characteristics as a phenotype, just like the purple flowers and the wrinkled seeds in the pea plants, which is to say that they can be passed on in the same ways from parent to offspring. And a way that we determine this in psychology is through experiments like in twin studies.
In twin studies, they take twins that are either identical, which is to say that they share almost 100% of the same DNA, and fraternal twins, which share more like 50% of the same DNA. And they look at different mental characteristics to see if there's a genetic basis for the identical twins to have similar types of behaviors or mental characteristics.
And they find that in some aspects, this is true. For example, identical twins tend to have more similar IQs than fraternal twins. And also, if an identical twin has autism, the other twin is 60% more likely to similarly have autism than fraternal twins are likely to have.
They also look at identical twins that are separated at birth, which occurs sometimes-- and obviously, that isn't an experiment that they can do, it's just something they can observe-- and to see if they have similar characteristics. And in some cases, they've found that to be true. Now, there's some doubt as to the results of these twin studies. But there's also evidence in them of the importance that biology can have on developmental psychology. So it's definitely an area of study that requires further research and understanding.
Genetic material for traits are transmitted from parents to their offspring; these biological influences represent the “nature” aspect of behaviors and cognition.
Genetic blueprint; genetic information is unique except for identical twins.
Located in the nucleus of each cell (46 total), made up of DNA and carry our genetic information.