Mendel's Experiments - Video Tutorials & Practice Problems
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Mendel's Experiments
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In this video, we're going to continue to talk about Gregor Mendel's experiments. And so Gregor Mendel used 2 different types of fertilization or gamete fusion in his experiments using either just 1 or 2 parent organisms. Now the very first type of fertilization that Gregor Mendel used in his experiments is self fertilization. And as its name implies, the organism is going to be fertilizing itself. And so it only involves one parent organism. And so self fertilization is when Gregor Mendel would apply pollen from a male organ to a female organ on the same plant. And so again, this is only going to involve 1 parent organism, and the organism would be fertilizing itself therefore calling itself fertilization. Now the second type of fertilization that Gregor Mendel used in his experiments is cross fertilization. And cross fertilization, unlike self fertilization, requires 2 parent organisms. And there's going to be a cross of gametes between these two, organisms. And so in cross fertilization, Gregor Mendel would cross pollen or apply pollen from a male organ to a female organ on different plants. And so again, this is going to require 2 parent organisms. And so if we take a look at our example down below, we can better distinguish between self fertilization and cross fertilization. And so over here on the left hand side notice that we're only showing you one single plant here, and so this is going to be self fertilization. When you can take pollen from the male organ and transfer it to the female organ on the same exact plant, and so that would be self fertilization. Now over here on the right, notice that we're showing you cross fertilization because we're showing you 2 plants, and notice that, pollen from the male organ of 1 plant is being transferred to the female organ on a different plant, and so this is called cross fertilization. Now moving forward in our course, when you see this arrow going across the 2 different plants, that's going to represent cross fertilization. And when you see arrows that loop back up onto itself, that's going to represent self fertilization. And so moving forward in our course, we'll talk more about Gregor Mendel's self fertilization experiments and his cross fertilization experiments. So I'll see you all in our next video.
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Self-Fertilization Experiment: True-Breeding vs. Hybrid Plants
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In this video, we're going to introduce Gregor Mendel's self fertilization experiment, which helped him distinguish between true breeding and hybrid plants. And so true breeding is highly linked to homozygous plants, And Gregor Mendel called true breeding plants plants that would self fertilize and produce offspring with the same phenotype as the original parent. Now hybrids, on the other hand, are highly linked to heterozygous organisms. And Gregor Mendel called hybrid plants plants that upon self fertilization would produce offspring with mixed phenotypes that are not always the same as the original parent. And so monohybrids, is just a term that refers to organisms that are heterozygous for just one specific trait or gene, and that's because the root mono is a root that means 1. And so again monohybrids are heterozygous for one specific trait or gene. So if we take a look at our image down below, we can better distinguish between true breeding pea plants and hybrid pea plants. And so notice over here on the left what we're showing you are true breeding pea plants. And so notice that we have over here on the left a homozygous dominant plant, that has 2 dominant alleles, 2 capital y's. And notice that this homozygous dominant plant is being self fertilized, meaning that it is fertilizing itself. And so in that scenario, we basically have a homozygous dominant being crossed with the same exact homozygous dominant. So we have 2 capital y's as the gametes, across the top and the sides of our Punnett square. And, of course, this creates organisms, offspring that have the same exact genotype and phenotype as the original parent. And so this is why all of the offspring are going to be yellow, and that means that this is part of true breeding. Now over here on the right hand side of true breeding, we're showing you a homozygous recessive plant that is green. And, notice that this homozygous recessive plant is being self fertilized, so we're having a homozygous recessive cross with another homozygous recessive, which is itself. And, of course, that's going to create offspring that are all homozygous recessive, all green offspring. And all of the offspring have the same phenotype as the original parent, which means that this is another example of true breeding. However, what Gregor Mendel noticed is that sometimes when he crossed yellow plants that they did not create, true breeding results. And so over here, notice that this is showing the hybrid plants. And the hybrid plants, turns out, are heterozygous, meaning that they have one dominant allele and one recessive allele. And even though they have a recessive allele, you can't tell just by visually looking at them because the recessive allele is being masked or hidden by the dominant allele. And so this plant appears yellow just as the homozygous dominant one would appear yellow. However, when you self fertilize this hybrid plant over here, what you get are results that are different than the true breeding results. And what you end up getting, of course, when you fill in this Punnett square, you get the homozygous dominant here, you get a heterozygous here, you get another heterozygous here, and of course you get a homozygous recessive in this last box. And so what you get is a mixture of offspring with the hybrids, and that's what we're showing you down here is that some of the offspring are going to be green. So you get a mixture of offspring, and that is how, these hybrids were identified. And so Mendel's discoveries using self fertilization intrigued him. He became fascinated by this. So what he began to do is cross fertilization experiments using pea plants where he would again take, pollen from one male plant and transfer that pollen to, pollinate or fertilize another, a plant of the female organ of a different plant. And so this here concludes our introduction to Gregor Mendel's self fertilization experiments and how he was able to distinguish between true breeding, plants that produce organisms that have the same exact phenotype as the parent, from hybrid plants that created a mixture of offspring upon self fertilization. So we'll be able to get some practice with this as we move forward in our course, and then we'll talk about cross fertilization experiments. So I'll see you guys there.
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Cross-Fertilization Experiment: Dominant vs. Recessive Alleles
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5m
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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 recessive alleles. 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 off offspring of crossing yellow and green pea plants, he noticed that he always found yellow peas in every scenario that he crossed 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 p plane. But then Gregor Mendel also realized that sometimes, Gregor Mendel would find a mixture of phenotypes 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 recessive trait. Now once again, sometimes, when Mendel found a mixture of phenotypes, that gave Mendel a clue that some of the yellow pea plants are going to be heterozygotes, and that they're going to have one copy of the allele for each of these traits. And so if we take a look at our image down below, we'll be able to see, Gregor Mendel's cross fertilization experiments. And over here on the left hand side, he's crossing a homozygous dominant yellow plant, with a homozygous recessive green plant. And, of course, when you set up the, the, punnett square for this, you'll put the, gametes of 1 parent on one side of the square, so we'll put the capital y's over here, And you'll put the gametes of the other parent on the top of the square, so we'll put the lowercase y's here at the top. And of course when you complete the Punnett square, what you'll realize here is that you're gonna have a capital y and a lowercase y, and that'll be the same for all 4 of the squares in the Punnett square. And so all of them are going to be heterozygotes, and heterozygotes all come out yellow. And so, when Gregor Mendel did these cross fertilization experiments, crossing yellow with green, a 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. And this is because it turns out that the yellow plants that he was crossing were hybrids or heterozygous, and, the homozygous recessive green plants were still homozygous recessive. And so of course when you fill out the Punnett square here, what you get is the capital y is going to be brought all the way across. The lowercase y here will be filled in, and then down below here you have all lower case y's. And so when he crossed a heterozygous yellow plant with a homozygous recessive green plant, what he saw was a mixture of offspring. He would get 50% yellow and 50% green. And so, once again, the fact that he never got all green when he crossed yellow and green pea plants, told him that the green must be the recessive, pea color. And, of course, the fact that he always got yellow no matter how he crossed yellow with green told him that the yellow color must be the dominant p color. And, again, he was able to get a clue that heterozygous 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.
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Problem
Problem
Mendel crossed a pea plant with yellow peas with a pea plant with green peas. All of the offspring created from this cross has yellow peas. What must be true about the parent plants of this cross for this to occur?
A
The parent with green peas was heterozygous for pea color.
B
The parent with green peas was homozygous recessive for pea color.
C
The parent with yellow peas was heterozygous for pea color.
D
The parent with yellow peas was homozygous dominant for pea color.
E
A and C.
F
B and D.
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Problem
Problem
You cross a pea plant with yellow peas (Yy) and a pea plant with green peas. How many unique genotypes are possible for pea color in the offspring? How many unique phenotypes are possible for pea color in the offspring?
A
2 unique genotypes; 2 unique phenotypes.
B
3 unique genotypes; 2 unique phenotypes.
C
2 unique genotypes; 1 unique phenotype.
D
1 unique genotype; 1 unique phenotype.
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concept
Generations of Mendel’s Plants
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4m
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In this video we're going to talk about the generations of Mendel's plants. And so Gregor Mendel standardized the naming system of generations to track inheritance patterns. And so really there are 3 generations that you all should be familiar with. And the very first generation is the parental generation. And the parental generation generation is commonly abbreviated as the p generation. And so this, of course, is going to be the original set of individual plants that are mated or the parents, if you will. Now the 2nd generation that you all should know is the 1st filial generation or in other words, the f one generation. And so the 1st filial generation or the f one generation is going to be the offspring of the p generation. And of course, the word filial is a word that's related to child. And so you of course, this is going to be the children of the parental generation. And then, of course, last but not least here, we have the 2nd filial generation or the f 2 generation. And this is going to be the offspring of the f one generation plants. And so let's take a look at our image down below to get a better idea of these generations. And so notice here in our first block, we're showing you the p generation, which is going to be the original set of parents that are mated. And so here what we have is a homozygous dominant pea plant being crossed with a homozygous recessive pea plant. And so, of course, when you set up their gametes on a Punnett square, like what you see here, you set up their gametes on the Punnett square and you fill in the punnet square, what you're going to get are heterozygous individuals in each of these punnet squares. In each of these squares, it's representing a heterozygous genotype. And so the individuals that are inside of this Punnett square represent the f one generation. And so that leads us straight down to this next part here. The f one generation, of course, is gonna be the 1st filial generation, the children of the parental generation. And, of course, because these, offspring, these children of the parental generation are all heterozygous, Of course, we're looking at heterozygous here. And so here we could either cross, fertilize a single heterozygous or, I'm sorry, self fertilize a single heterozygous or we could cross fertilize 2 heterozygous. Either way, we're going to have the heterozygous alleles of the gametes across the top. And when we fill this in, what we will have is this right here. We will have 1 homozygous dominant, 2 heterozygous, and 1 homozygous recessive, and these are the possibilities of the offspring. So these squares within here represent the f 2 generation, and that leads us to the next, square that we have down here. The f 2 generation is going to be, as you can see here, 3 3 of the 4 possibilities are going to be, yellow. So you can see these three possibilities here are yellow. And one of the possibilities of the f two generation here would be green. And so, the generations are just referred to as p generation, f 1 generation, or f 2 generation. And so this here concludes our introduction to the generations of Mendel's plants, the p, f 1, and f 2 generations, and we'll be able to get some practice applying this as we move forward in our course. So I'll see you all in our next video.
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Problem
Problem
In the study of genetics the offspring of the parental generation is referred to as the: