 Let's solve a couple of problems on dihybrid cross. We're given it a pea plant, tall is dominant to short and yellow peas are dominant to green peas. A tall plant with green peas with this particular genotype is crossed with a short plant with yellow peas with this particular genotype. What is a chance that the offspring will be short with yellow peas? Now I know the first time you look at it, it might seem like, oh my God, there is so many things happening, but if you do it step by step, it'll all make sense. The first thing I like to write always is the genotype of the parents that are being crossed. And that's easy here because it's directly given. So we're given a tall plant with green peas. This is being crossed with this. So let's start by writing that down. So this, this is a tall plant. Why is it tall? Because even though it has both these leaves, tall is dominant and therefore it appears to be tall. Why is it green? Because look, it has both recessive green color alleles. Therefore it is green. On the other hand, this one, look, why is it short? Because it has both recessive short alleles and therefore it is short. And why is it yellow? Because it has one yellow dominant allele and therefore it is yellow. So it makes sense. If you think about it for a while, it all makes sense. Now the question is what will we get when we cross them? How do we figure this out? Because we have two traits and they're both hybrids. That's why it's called dihybrid cross. How do you do this? Well, we use something called the independent assortment law, which basically says that when sperms and excels are formed, the alleles of the height and the alleles of the color, they assort independently. Here's what I mean. So let's say that this is the one that has the sperms and this is the one that has the eggs. So if I look at the sperms, this tall, this capital T could combine with this small Y and I could get one sperm like this. Similarly, this capital T can now combine with this Y to get another sperm like this. But you can also have this small T combining with this Y to get this sperm. And you can have this small T combining with this Y to get another one. So what we are seeing is we're looking at all the possible combinations because they assort independently. You get what is that? What I mean? The height and the color alleles are independent of each other and therefore they assort independently. Now similarly, what will it be for the eggs? Why don't you pause and write that down yourself first? Okay, let's try. So we will have this T combining with this Y, this T combining with this Y, this T combining with this Y and this T combining with this Y. And there you have it. Once you've written this down, then you can draw the table and then you can write down all the combinations and all the things. Again, why don't you pause the video and write it down yourself and then I'll show you the whole table and then you can compare with what you've got. All right, here we go. This is the table that we eventually end up with. And again, here the place that will go wrong is just because we need to be just careful about capitals and short-wise, but otherwise it's basically just combining them. All right, now that we have this, let's look at our question. What is a chance that the offspring will be short with yellow peas? So what are we looking for? Short means you need both small T and yellow means you should have at least one capital Y because that's dominant. So let's look for it. So we need both small T's, so it's not here, so it's not here, or we have here and here. Now in this, we need at least one capital Y because we want yellow. So we have one capital Y, we have one capital Y here. So these two will work for us. These won't, these two will work for us. So these four are the ones that are gonna give me short with yellow peas. Two capital Ys would have also worked, but I don't have two capital Ys. See, it's not there anywhere. So I need at least one capital Y and that's what I get. And so what is the answer? I get four out of total 16. So my answer is four out of 16, which is one by four, but if you want that in percentages, it'll be multiplied by 100, I get 25%. So there's a 25% chance that the offering will be short with yellow peas. Okay, let's do one more. Why don't you pause the video and see if you can try this yourself first, the whole problem. Okay, let's do this. But given in snakes, being rude is dominant to being respectful. I need to tell you that this is a hypothetical example. It's not real that you don't have being rude or respectful has anything to do with connection with genes. So it's just a hypothetical example, okay? And being sneaky is dominant to being sincere. So what we're given now is a female snake, which is homozygous recessive, is mated with a male snake, which is homozygous dominant for both. Okay, so let's write that down. What does it mean to say female snake homozygous recessive? Homozygous means both are the same. So for both the genes, it has the same alleles and it's recessive. So both will be small r and both will be small s. And similarly, it's given that for males, it is homozygous dominant. So both will be capital R and both will be capital S. Homozygous, same. So this is what is being happening. Now, to figure out what's gonna happen with the offspring, what we're gonna do is the same thing. We're gonna write down what the sperms and what the excels are gonna look like. This is the male. So can you write down the sperms and the excels yourself? So this is the sperms, these will give you the sperms and these will give you the eggs. And yeah, we just need to make sure that they're assorted independently. Okay, so for sperms, you get this r combining with this s, this r combining with this s. Hey, you're gonna get the same thing. This r combining with this s and this r combining with this s. You'll get all of the same thing. And similarly, r combining with s, r combining with s, all of them will be recessive. We'll get the same thing. So can you see all combinations will be exactly the same? Exactly the same. You'll have capital R small r, capital S small s. Which means all of the offsprings are going to be capital R stands for being rude. That's dominant, so they'll be rude. And capital S stands for being sneaky, so they'll be dominant. So all the snakes will be rude and sneaky. What do we want? We want them to be respectful. We want to see how much of them will be respectful and sincere. None of them will be respectful and sincere because for being respectful, you need both small rs because it's recessive. And for sincere, you need both small s because it's recessive. So that's not possible anywhere over here. And so our answer is zero.