 Let's solve a few problems on monohybrid cross. Here's the first one a farmer mates a cattle with horns to a heterozygous Cattle without horns. Let's quickly draw that mates a cattle with horns to a cattle without horns Okay Now if no horns is the is dominant to horns That means the gene or the allele that's responsible for no horns that is dominant to the allele That's responsible for giving horns. What is a chance that the offspring has horns? We need to figure out what is a chance that the kid will have horns. All right How do you do this? My first step is to first write down the genotype meaning write down what the alleles look like Well for this one, it's easy. It's given that it's heterozygous heterozygous means one capital N one small n So for this one, I know it is one capital N one small n and It makes sense because it has one capital N. That's why it's dominating and it's not getting any horns What about this one? It's not mentioned whether it is homozygous or heterozygous Well, it doesn't have to mention it because the only way you can have horns is to have both of them small n You need both alleles to have horns because they are recessive Think if you had one capital N Then this wouldn't have any horns because that would dominate. So the fact that horns is recessive Automatically means that the only way to get this is to have kept small n small n Okay. Now to figure out what the offspring would look like Let's use the law of segregation. The law of segregation says that when gametes are formed, which is sperms and exels are formed Then some sperm cells will get this one other sperm cells will get this one Some exels will get this one other exels will get this one. All right, so let's draw that So we have the subsperm cells or both the sperm cell will get n and n small n small n What about exels some exels will get this capital N some exels will get small n and now we can do the table Great idea for you to pause the video complete the punnett square. This is called the punnett square Complete this table and see what the answer is going to be All right, if this sperm fertilizes this egg We get capital N small n if this sperm fertilizes this egg We get again small capital N small n if this sperm fertilizes this egg We get small n small n and this sperm fertilizes this egg We get small n small n and now let's see Wherever there is a capital N because it's dominant. We will get no horns. So we'll get no horns here No horns here. These are both recessive will get horns here Horns here and so you can see we have two out of four Offsprings who will get horns So the answer is two out of four But if you want that if if you if you want it to be into percentage you multiply by 100 to get 50 percent So there's a 50 percent chance that the offsprings will have horns All right, let's do one more. All right. Why don't you try pausing the video and see if you can solve this entire question yourself Okay, we are given that in muscles brown coloring B is dominant and blue coloring B is recessive a Homozygous brown muscle crosses with a blue muscle. So let me just directly show that a brown muscle crosses with a blue muscle What percentage of offsprings are expected to be blue? Again, the first step is to try and figure out what the genotype is So i'm given that in muscles, uh, okay, it's given that a homozygous brown muscle Since i'm given its homozygous both the alleles must be same. So brown muscle. So this must have both capital B capital B What about this one? It's not given whether the blue muscle is homozygous or heterozygous But just like in the previous case since blue coloring is recessive The only way to get a blue muscle is if both the alleles are blue So that means it has to be small b because even if one allele was capital B brown Then the whole thing would dominate the brown would dominate and this would have become brown So you understand that right? Okay So now that we have the genotypes now we're going to use the law of segregation to first draw the penet square So for example, if this is the male and let's say the sperms are coming from here Then the sperms will get capital B and capital B because both are capital B And if this is the female if this gives you the eggs then both the eggs will give you small b and small b And now if we do the punnett square, what would we get? Well, the this sperm when fertilizes with this egg you get capital B small b In fact, you'll get the same thing here as well When this sperm fertilizer you get the same thing everywhere So everywhere you get uh The same thing the genotypes is the same And therefore what you end up with since capital B is dominating. Hey all of these will end up giving you brown mussels And therefore you get hundred percent brown mussels, but what is asked is what is the percentage of blue? Well, if everything is brown then you get zero blue. So the answer is zero percent offsprings will be blue