Cross-Fertilization Experiment: Dominant vs. Recessive Alleles

by Jason Amores Sumpter
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In this video, we're going to introduce Gregor Mendel's cross fertilization experiment, which helped him distinguish between the dominant and the recess of a Leal's. And so Gregor Mendel discovered dominant and recessive traits when he cross fertilized yellow pea plants with green pea plants. And so, when analyzing the offspring of crossing yellow and green pea plants, he noticed that he always found yellow peas. In every scenario that he crossed the yellow with green pea plants, he would always find yellow. And so this told him that the yellow color must be the dominant trait if it's always showing up in every scenario that he crosses a yellow and a green pea plant. But then Gregor Mendel also realized that sometimes Gregor Mendel would find a mixture of FINA types where he would find yellow and green offspring. But Gregor Mendel never found all green offspring when he crossed yellow and green pea plants. So this told him the fact that he never got all green offspring, that the green trait must be the recess it trait now, once again, sometimes when Mendel found a mixture of FINA types, um, that gave Mendel a clue that some of the yellow pea plants are going to be hetero. Zico's on that. They're going to have one copy of the illegal for each of these traits. And so, if we take a look at our image, down below will be able to see uh, Gregor Mendel's cross fertilization experiments. And over here on the left hand side, he's crossing a homo Zegas dominant yellow plant with a homo Xigris Recess Ivo Green plant. And, of course, when you set up the the Pundits Square for this, you'll put the gametes of one parent on one side of the square. So we'll put the capital wise over here and you put the game. It's of the other parent on the top of the square, so we'll put the lower case wise here at the top. And, of course, when you complete the Pundits Square, which will realize here is that you're gonna have a capital Y and a lower case, why? And that will be the same for all four of the squares in the pundit square. And so all of them are going to be hetero zygotes and hetero zygotes all come out yellow. And so when Gregor Mendel did these cross fertilization experiments crossing yellow with green. Ah, lot of times he would just get all yellow offspring. But then sometimes when he crossed yellow with green pea plants, he wouldn't get all yellow offspring on. This is because it turns out that the yellow plants that he was crossing were hybrids or hetero zegas. And, uh, the homos, August recess of green plants were still homo zegas, recessive. And so, of course, when you fill out the pundits square here, what you get is the capital. Why is going to be brought all the way across the lower case? Why here will be filled in and then down below. Here you have all lower case wise. And so when he crossed a hetero zegas yellow plant with a Hamas, I guess recess of green Plant. What he saw was a mixture of offspring. He would get 50% yellow and 50% green. And so, once again, um, the fact that he never got all green when he crossed yellow and green pea plants told him that the green must be the recess. It p colored. And of course, the fact that he always got yellow and no matter how he crossed yellow with Green told him that the yellow color must be the dominant p color. And again, um, he was able to get a clue that hetero zig it's existed when he saw this mixture of offspring. And so this year concludes our introduction to Gregor Mendel's cross fertilization experiments, and we'll be able to get some practice applying the concepts that we've learned as we move forward in our course, So I'll see you all in our next video.