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Genetics

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1. Introduction to Genetics

History of Genetics

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History of Genetics

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Hi in this video, we're gonna be talking about the history of genetics. Okay. So I know if you're anything like me, history is not probably your favorite subject. That's okay though. But history and genetics for some reason is really important. The professors of genetics really like hitting you with history questions. So throughout the whole semester, if I'm giving you dates and names and people and to tell you know, these names are important. These dates are important. These concepts are important because for some reason geneticists love to test and quiz you on history. But for this we're going to start way back. I mean like the very earliest time that I think you'll probably ever even talk about in a science class. And that is, you know, Bc 8000 to 1000 Bc. And this is when genetics really first came about. Not the genetics we know today, but really the genetics that they had then was things like domestication and that's domestication of animals. Things like, you know, the wolves to dogs, domestication, its cultivation of plants um that they could eat and harvest and raised as people started, you know, grouping together, living together. They needed food sources, they needed animals and so they domesticated things. And so this type of genetics is actually called selectively breeding or artificial selection. And essentially this is the process of taking organisms with certain traits and making them together to propagate that trait. So although carrots didn't really exist in the same way back then. But if you had an orange carrot and you wanted more orange carry. That's what you would do is you would sort of make orange carrots together and you'd keep getting orange carrots for dogs. You take these gentle wolves and you make them together and eventually over time they turn into these gentle dogs which are completely different species. But this is this type of breeding. You're selecting for certain traits at the time though, I mean obviously no one knew at all what controlled this. They had no idea. They were hoping that, you know, you make two orange carrots together, you get another orange carrot but they didn't know right. And sometimes you don't. And sometimes there are these unique genetic traits that will talk about where if you make two orange carrots together, sometimes you get a purple carrot and these types of genetics, they had no idea how to control but they did their best. And so they were like, you know, most likely this will work. So that's what we're going to keep doing. And so they use the principle like the gets like so things that are like will keep producing those things. So orange carrots will likely keep producing orange carrots. And so here's some carrots for instance that have undergone artificial selection so that you can get all these different colors, They're pretty much all the same size but all these different colors, you know, were bred for that trait or for some trait that gave them these colors example of sort of artificial selection. Now we're going to jump forward a lot further. So now we're in 300 B. C. And this is when Aristotle and the Hippocratic School of medicine started coming about and saying proposing some theories about how you know inheritance work. They could see that you know Children often looked like their parents but they really had no idea how that happened up until then all they had was like against like. So what they did is they proposed this idea this pan genesis and this uses these particles called mules and mules. They believed were these particles that existed in every part of the body. So there were brain ones. There were I jim mules. They were hand daniel's leg, Daniels, kidney Daniels, all these mules that existed in every part of the body and they traveled to the reproductive organs. And so when they made it to the reproductive organs, these gym mules were then able to be passed on to the offspring. And that is what allowed Children to look like their parents. But this allows for something interesting including the inheritance of acquired characteristics. So for instance, if a man is a really great musician and so he spent his whole life acquiring this musical talent, then he'll have these special musical gym mules in his body and that those would travel to the reproductive organs and be transferred to the offspring giving that offspring a much higher chance of being really great at music. And so that's what they believed here. So here's an example of what this looks like all these little circles that had the gym meals. And you can see there's some here some in the brain and choose a different color. I chose black. Let me choose red. There we go. There's some in the leg all over and they all travel to the reproductive organs. They get into the eggs and the sperm and then that is going to be passed on to the offspring. So that was kind of the theory at the time. And that actually remained for a very long period of time. Because now we're going to jump ahead to 1650 and 1850 or through 1850 a. D. And this is when two more theories of inheritance came about. The first is epic genesis. And this says that organisms, our offspring are derived from substances found in the sex cells are found in the sperm or egg. Now this is actually almost right. I mean it is right right. They didn't know what these substances were. But they said you know the sex cells contain the information to make the offspring. So this was actually very intuitive. But the conflicting theory at the time was this theory of pre formation. And it's kind of one of my favorite scientific theories of all time because I think it's just absolutely ridiculous. And I know that I shouldn't make fun of people from this time period. but it just blows my mind. So pre formation said that the sex cells contained this um this structure called Hama Oh jeez Homan Oculus, which I have a difficult time saying, but anyways there it is and essentially what it is is a miniature adult. There's just a little little, I mean just such tiny adult that will grow into a few full human. So what it looks like because this is a drawing of sperm and you can see right here there's a little tiny person just like balled up inside, like just sitting in there waiting to come out and eventually it keeps growing, keeps growing and becomes a baby which eventually becomes a volatile human. So this is what was believed at the time and you know, don't make fun of people but dear goodness! This this idea is a little ridiculous, but that's what they believed. It's kind of my favorite theory of all time. Um So the epic genesis was much closer but actually most people at the time believed in the pre formation versus that genesis and then came Gregor Mendel and I know all of you guys have heard about mental, he was this Australian monk and he began studying pea plants during the 18 hundreds. And so he was, he was so crucial in getting or providing us with the information that is genetics today. And so at the time Mendel was studying what people were believing is this idea of blending theory of inheritance and this says that Children were a blend of their parental traits. So all the traits were kind of like fluids and you mix them together and that created the offspring. So it's kind of like paint, you mix red paint and white paint together. Then the offspring would be the pink paint be a mix. And this is what was the major theory at the time. Mendel was doing his research but he actually ended up disproving this because he would make purple pea plant flowers and white p plant flowers and they didn't turn into like a light purple. They either were purple or white. So there wasn't that mixing that the blending theory of inheritance predicted. So what Mendel did is he actually after all of his studies were we'll talk about a lot more like it's just excruciating detail in future lessons. But he proposed that there were particles not fluid, so it wasn't just like paint, that liquid paint, it was actual particles. And these particles controlled heredity. They controlled inheritance. And so today we now know that these particles are called jeans at the time they called them particles. And so he proposed a few things and we're going to talk about more in detail these proposals and future topics but he proposed that there are two copies of each particle which we now know are called the wheels. But I'll get into that in other videos and each of these copies control one trait. So for instance, color two copies of these particles control one color trait. And then he proposed that one is more dominant than the other. Um and the dominant one actually true chooses what you see. So what you see here is it's kind of hard to see. You have a purple and you have this like light pink one here and I'm gonna circle it in case you can't see it. So the blending theory of inheritance says that if you mix this purple ball with this light pink ball, what you'll get is this light purple one. But Mendel didn't see that. What he saw is that if you mix up, if you made a purple and light pink together, what you get is you either get purple or light pink, you don't get this blending the blending theory, you know, couldn't couldn't be right. But unfortunately Mendel, like he published his work in 1866 but generally was largely ignored and pretty much forgotten about for about 40 years. And then in the 1900s, there was this guy called William Bateson and we'll talk about him more in the future. But um he, as well as some other scientists at the time, actually rediscovered Mendel's work and they did experiments and proved, you know, this guy wasn't just some guy we forgot about um this this stuff really means something. And this is when the term genetics was actually coined for the first time. And then you have this another scientist which we're going to talk about a lot more in the future Thomas Hunt Morgan's Thomas H. Morrigan and he actually found, or it really discovered more of the mechanism of how this works, how, how these particles of these genes were inherited and he found that they were inherited on chromosomes. And he actually proposed the chromosomal theory of inheritance in 1910. So these names I'm throwing out here, you will need to know them and their dates and everything, but we're gonna talk about them more in future topics. But for now, just know that this is kind of the step all the way from, you know, just domesticating dogs. Light begets light through pre Formation of the tiny human and the sperm and then to Gregor Mendel, who was actually proven and remembered and rediscovered in the 1900s. And now we have genetics today. So that's just a brief overview of the history of genetics. So now let's move on
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Problem

Match the following inheritance theory with the appropriate definition. 

I. Pangenesis                                   _________ 

II. Epigenesis                                   _________ 

III. Preformation                               _________ 

IV. Blending Theory of Inheritance _________ 


A. Children were derived from substances found in the sex cells 

B. Children are a blend of parental traits 

C. Sew cells contain a miniature adult, which will keep growing until adulthood 

D. Gemmule particles were carried from different body parts to reproductive organs

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3
Problem

Which of the following terms describes the process of breeding organisms for certain phenotypes?

4
Problem

Mendel proposed that ___________ controlled inheritance?

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