Okay. So now let's talk about a few terms that we use to describe things in genetics. The first is sort of an end on an individual level. We can say that an individual has a certain genotype. What we're referring to with the genotype is the set of alleles. These are going to be the actual alleles for a given trait. For instance, if we want to know about hair color or eye color, then the genotype is going to be which alleles you have. The phenotype is different; it doesn't necessarily care what alleles you have; it just looks at what you look like. So, if we're looking at hair color, it could be blonde, brown, black, red, any of these hair colors; that's the phenotype. You can't actually see the genotype; you have to know what alleles you have. Genes present themselves in many different types of traits. We have morphological traits which are things that affect appearance, like skin color, feather color, height, or size. Then we have physiological traits that affect the ability of an organism to function properly. For example, the shape and function of the lungs can help with the physiological aspect of taking in air and breathing. We also have behavioral traits that affect how organisms respond to their environment. It's harder to think of for humans, even though it exists, but it's easier to consider different mating dances that birds or other organisms perform. When reading about this, you'll notice that the male does some kind of fancy mating dance to attract the female. These are actually behavioral traits that can be inherited through genetics.
Looking at this further, you can see the phenotype is yellow or green, and the genotype is presented here. These refer to different types of alleles. The uppercase letter represents a dominant allele, which you're going to see if it's present, and the lowercase letter refers to something that's recessive, which you'll only see if the dominant is absent. Don't worry if you don't necessarily remember dominant and recessive now; we'll go over this in much more detail. But I just wanted to get you to understand that the phenotype is what you see. The genotype is what you can't see, but we're going to spend a whole semester learning how to actually figure it out.
There are three divisions of genetics. First, there's transmission genetics, which studies inheritance and the ability to pass traits onto the next generation. Then you have molecular genetics, which studies gene activity at the molecular level. Examples of this are DNA replication, transcription, or translation. These are molecular genetic events. Finally, you have population genetics, which studies genes in terms of an entire population. So if we take the entire population of the United States, we can compare traits and genetics with people in Australia or Kenya. These types of population genetics studies will be discussed towards the very end of the semester.
With that overview, let's now turn the page.
