Hi. In this video, we're going to be talking about Mendel's experiments and laws. Okay. So, Mendel is Gregor Mendel. He was an Austrian monk, and he studied genetics and is really mainly the founder of genetics. And his main focus was pea plants. And the reason he chose pea plants was because you can breed them, you can breed a lot of them, you can breed them easily, but also there were a lot of pure lines available. So what is a pure line? A pure line is going to be when all of the offspring from that line produces another pure line. So that means that the trait that you're looking for will be identical in the parent and in the offspring. And so, for instance, a yellow seeded pure line will produce yellow seeded offspring if, you know, if they're mated together. Pure line with another yellow seeded pure line, it's going to produce yellow-seeded offspring. And so that was a major reason why Mendel chose pea plants because you can you know, you know what your offspring is going to be if you use these combinations. And so that allowed him to make combinations of pure lines to see what happened. And, he was very meticulous, when doing these studies, and he labeled each generation in a very specific way. And, it's important that you understand what these terms and these labels mean because this is how you're going to understand everything in genetics from now on. So, the first is the parental generation, and this is the first mating that occurs, the very first one. Male and female are plant and another plant, this is what happens. The offspring of that mating is the first filial generation or F1, which is what you'll pretty much always see it as F1, and this is the offspring produced from the parental mating. Now when you have an F1 generation, there's lots of things you can do. You can self-mate them. I suppose with plants, with certain sexually reproducing or certain organisms, you can't do this. Like, with humans, you can't do it. But with plants, you can self-mate. And that means that the plant pollen can be used to fertilize itself. Self-mating is a technique that Mendel used and still a lot of geneticists use today. You can also cross-fertilize them, which means that one plant's pollen is used to fertilize another plant. Obviously, we're talking about plants because we're talking about Mendels, but you can do this with other organisms as well. So when you have your F1 generation, you can self-mate it, you can mate it with another F1, you can mate it back to its parent. You can mate it with anything you want. And, generally, what will happen is the second filial generation will be produced, also, shorthand F2 generation. This is the offspring from the F1 mating. So, those are the 3 generations. Now, let's go through one of Mendel's crosses as our example. So, here we have the parental generation. You can see that he took yellow seeds and green-seeded plants and crossed them. So, here's the parental. The offspring of that is called what? Offspring of that parental mating is called what? Called the F1 generation. And what Mendel saw is that when you mated the yellow seeds with the green seeds, you got all yellow seeds in the F1 generation. Then what he did is he took the F1 and he self-fertilized, meaning that he self-fertilized them. So he took the pollen from that F1 plant and used it to fertilize the same F1 plant. When he did this, he saw not only yellow, but he also saw green in this F2 generation. So, we went from parental F1 and F2. So, now we're in the F2 generation. And, so, he started to count the number of these plants and to figure out, you know, what ratio. Is it mostly yellow? Is it mostly green? You know, what's going on here? And, what he saw is that there were 6,022 yellow plants and 2,001 plants, which equals a total of 8,023 total F2 plants. Now if you do ratios, so if you do 60228023 and you do 20018023, what you'll get approximately is 3 fourths and approximately 1 fourth. Now, it's not perfect, it's never perfect in genetics. It doesn't have to be exactly perfect but that's approximately what you'll get. And so he noticed that this was a 3 to 1 ratio, and that this ratio kept popping up a lot, and this will become very important and we'll talk about this ratio more. But this is just an example of one of Mendel's crosses. So then he took the F2 generation. So here we're dealing with this one. So we have yellow and we have green. So he took each one of those. So he took a yellow plant and then made the F3. So you're getting the pattern here. So we went from parental, we went from F1, F2, and then now we're at F3. Now, most of the time in this class, we're going to stop at F2, but just for this example, we're going to keep going through F3. So in F3, he took a yellow F2 and selfed it. So he took a yellow F2 and took that pollen and fertilized that same yellow F2 plant. And what he found is he saw this 3 to 1 ratio again of yellow and green plants, but when he did the same thing with the green F2 plant he got 100% or 4 out of 4 green plants. So that was this is a really important cross to know what Mendel did. So make sure you go back and review and you understand each step of this process. So this is one major cross that he did. Parental, F1, all yellow, then he got the F2, which was 3 fourths yellow and 1 fourth green. Then he took each of those F2 and selfed them and got different ratios. Then he did a second cross and what the second cross was was a yellow F1, This is from the F1 generation and a green. And when he mated the yellow F1 with a green, what he saw is that half the offspring were yellow and half the offspring were green.
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Mendel's Experiments and Laws
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