Introduction to Traits and Heredity

Okay, so since I stopped writing on this blog a while ago, a lot has changed. Namely, my name. (Pun intended.) I prefer to be called Brighid now, (pronounced BREE-id) and this blog will reflect that. With that in mind, here is an essay on traits and heredity. I’m putting this up, (and the essay after it) because while psychology is easy to understand without too much background, genetics is something that won’t make much sense at all unless you start at the very beginning. And so, without further ado;

 

Introduction to Traits and Heredity.

A lot of us have wondered at some point where we might get certain traits from. Why you have brown eyes like your father but not blue eyes like your mother, why you’re taller than your mother but still shorter than your father, or why both your parents have brown hair and you have red. Well, it all boils down to the genome.

                A genome is basically like a set of instructions, telling your body what to do, what to build. And since each cell follows a different set of instructions, infinite variations are possible. Different genetic codes create different traits, such as red vs. brown hair, or tall vs. short. Or personality traits, like nice vs. mean, or patient vs. impatient. Of course, certain traits have more to do with the environment than anything else, but we’ll get to that later.

                There are many, many different traits to choose from when talking about the genome. So that’s why we like to categorize them into neat little boxes; physical vs. behavioral, visible vs. hidden, and innate vs. learned. But let’s not forget the number one rule of the scientific world; almost nothing fits in a neat little box. So there are certain traits which are easy to define. Say you happen to be very tall. Height is something that can definitely be classified as physical, visible, and innate. But what about something like intelligence? Well, it could definitely be behavioral – intelligence definitely affects the way we interact with the world – but it could also be physical. Why? Because intelligence can also be defined by the number or pattern of neuroconnections in the brain. What about visible vs. hidden? Well, at first glance you would classify intelligence as a hidden trait. You can’t just look at someone and tell how smart they are. But what if we’re speaking in the context of the products of said intelligence? If you knew that someone you were talking to had won a Nobel Prize, their intelligence wouldn’t be very “hidden”, would it? And as for innate vs. learned, there is still debate about how much intelligence can be learned. So as you can see, this kind of categorization can be tricky, not to mention dangerous; it wouldn’t do to make false assumptions that could mean a lot to the scientific community.

                But let’s think about something; where did all these genes come from? The answer is simple; your parents! But wait… weren’t we talking earlier about the child who had red hair, even though both their parents had brown hair? Maybe it isn’t as simple as it seems.

                People have been puzzling over this pretty much since humans began. Perhaps you know of a fellow named Hippocrates? Hippocrates was a nature philosopher, who studied the mechanisms of inheritance. He had a theory called Blended Inheritance. He saw that the male reproductive organ had a fluid that it produced when it was in the process of, well, reproducing. He theorized that females must have a similar fluid, and that each fluid carried a plethora of genetic material. Some from the eyes, some from the toes, some from the hair, etcetera etcetera. His idea was that when the fluids met, there was a “battle of the fluids”, and the genetic materials from each fluid which remained victorious would be the ones which made up the new human. Well, okay. There are some obvious flaws in that theory, but it seems pretty solid. Except, wait… it explains why a kid might look more like mom than dad or vice versa, and even explains how a child might be a near-perfect blend of the two. But what about our little redhead from earlier? This is where a fellow named Gregor Mendel comes in.

                Gregor Mendel was a monk, living in Austria in the early 1800s. And he had a bit of a hobby; he liked to study genetics. Of course, if you’re studying genetics you’re going to have to study reproduction at some point, and his bishop didn’t particularly like him studying animal sex. So he switched to pea plants instead.

                What he discovered was truly fascinating; Hippocrates had been thinking of genetics like pails of paint. If you have one pail full of red paint and one full of white paint, you can mix the two however you like, but you’ll always come out with some variation of the two colors. Of course, you can get lighter or darker pinks, or even colors that look almost totally red or white, but there’s no chance of a new color. But Mendel had a different idea; he had the idea of particulate inheritance.

                The idea here is that each parent has two genomes, a working set and a hidden set. When the parents get together to make a baby, they each have a chance of passing down some of the hidden set, and some of the working set. Of course, the hidden set is also hereditary; any trait you see in yourself that you don’t see in your parents was a working set at some point in your family line. But this can explain our little redhead; most likely a grandmother, or someone in the family, was a redhead. But the gene was hidden until it collided with more hidden-redhead genes from the other parent. Now, keep in mind that these hidden genes won’t come into play unless they are contributed from both parents. If our favorite carrot-top had gotten even one set of brunette genes, from mommy or daddy, her hair would have come out the same color, the gene remaining hidden.

                But there’s more. Enter Mr. B.F. Skinner, a psychologist in the mid-1900s. You may be wondering, what does a psychologist have to do with genetics? A lot, as it turns out. Skinner did a lot of experiments with operant conditioning. In one, he would place a rat in a cage with a lever, a red light, a green light, and an electrically wired floor. If the rat pulled the lever while the green light was on, food would be dispensed. But if the red light was on and the rat pushed the lever, it would receive a mild electric shock. In time, the rat would learn to pull the lever only when the green light was on. And through his experiments, Skinner found that the environment can have quite a lot to do with how these traits manifest. This is the classic nature vs. nurture situation, which makes it a lot harder for geneticists; now, alongside all that visible vs. hidden, physical vs. behavioral, and innate vs. learned from earlier, we also have to work to find out whether a trait is something an individual was born with, or something they learned. Or even if the environment took an innate trait and modified it.

                That, my friend, is the basics of genetics. Just the basics. Genetics is a very diverse and complicated science, and can’t possibly be covered in one essay. But let’s see what we can do with a couple.