In this video, we're going to talk about how to use Punnett squares, which it turns out that it is a 3-step process to using Punnett squares. Now we're going to be making a Punnett square for these 2 pea plant individuals from our last lesson video. This pea plant over here, which is homozygous dominant because it has 2 dominant alleles or 2 uppercase Ys, and this pea plant over here which is homozygous recessive because it has 2 recessive alleles or 2 lowercase Ys. And so we'll be able to create a Punnett Square for these two organisms. And so in the very first step of creating a Punnett square, step number 1, of course, you have to draw the square itself, which is going to be a square, with 4 squares within it. But then after you draw the square, you are going to simply align the alleles of the parent gametes on the top and the left side of the square. And this is going to represent the process of meiosis, and recall meiosis is gamete formation. And so notice in step number 1, again, all we're going to do is align the gametes of the parent on the top and the side. And so notice that parent number 1 up above here, is, homozygous dominant, it has 2 capital Ys. So when it undergoes meiosis, each of the gametes can only have a capital Y, one capital Y. And for this parent number 2 over here, which is homozygous recessive to lowercase Ys, each of its gametes can only have one lowercase Y, which I'll draw with a lowercase cursive here to distinguish it easier from the capital Y. And so that's it for step number 1, align the alleles of the parent gametes on the top and left side of the square representing meiosis, gamete formation. And then in step number 2 of using the Punnett square, all we need to do is actually just fill in the Punnett square itself. And this process is going to represent fertilization or the fusion of the gametes. And so, when we take a look at the square this first square over here at the top left, this one's going to represent the fusion of this gamete with this gamete up here at the top. And so what we need to do is, bring down those, fill in these gametes. So this capital Y here is gonna go in this position and this lowercase Y here will go in this position. And that represents again the fusion of these 2 gametes right here in this box. So that represents fertilization. But then what if this gamete fuses with this gamete over here? Well, then we need to fill in, this box right here. So that would be bringing down this capital Y to this position and bringing across this lowercase Y over to this position over here, And so we would get this combination. And then of course this box down here represents the fusion of this gamete with this gamete here at the top. And once again you just bring down the capital Y here to this position, and you bring across the lowercase Y here to this position. And then, this last box over here represents the fusion of this gamete with this gamete here at the top. And so again, all you need to do is take the capital Y here and bring it all the way down, and bring the lowercase Y here and bring it all the way across. And so now what you can see is that we've completely filled in each of these 4 squares within our Punnett square. So we've completely filled in our Punnett square and we've completely finished step number 2, which again represents fertilization or the fusion of gametes. And so step number 3 here is really just to analyze the results, or in other words, analyze the possible genotypes and phenotypes of the offspring. And so when you take a look at step number 3 over here, analyze the results, of each of these squares, what you'll notice is that each of these 4 squares is showing a heterozygous genotype, 1 dominant allele and one recessive allele. And so, recall that the dominant allele, the capital Y, is going to dominate over the recessive allele. So that means that the capital Y, the yellow allele, is going to dominate, and each of these squares here represents a heterozygous yellow offspring. And so what we can say by analyzing the results is that there are 4 possibilities for yellow phenotypes in the offspring, and there are 0 possibilities for green phenotypes in the offspring. Again, to get a green phenotype, one of these squares would have to have 2 lowercase Ys, but that is not the case here. And so what's important to note is that each of these squares that you see here represents an equally probable genotype and phenotype that one single offspring can inherit. So these represent the possibilities. And so, later in our course, we'll be able to talk more about calculating probabilities when it comes to Punnett squares. But what's really important to note is that each fertilization event producing an offspring is going to be independent of each other. And so one fertilization event will not impact another fertilization event. And so that's exactly what we mean by independent. One fertilization event does not impact another fertilization event, which technically means that for each fertilization, for each offspring, this Punnett square would need to be reconsidered and redone essentially. And, again, we'll get to talk more about probabilities as they apply to Punnett squares later in our course. But for now, this here concludes our lesson on how to use Punnett squares, and we'll be able to apply these concepts as we move forward in our course. So I'll see you all in our next video.