 Close signs thirties. Let's take a look at this genetics practice handout that I've got for you to work on today There's a lot of terms and definitions here So if you haven't had a chance to check out the genetics terms matching handout, that's a good idea Especially if you haven't gone through any of this material in a previous class before In this video, we're gonna go through questions one two and six But if you had questions about any of the other problems this handout, let me know and I'm happy to help you out Let's start off with the first one here mono hybrid crosses So in tomato the allele for red color Capital R is dominant and for yellow. It's lowercase R So first of all allele is referring to these letters. We're talking about here. All right, so this is one allele that's another allele it's sort of one way that a gene can come out and The capital letters always mean dominant and the lowercase letters mean recessive in this case If you have a capital letter you end up being red for this tomato So we're gonna write out a genotype, which is a combination of these letters for a heterozygous hetero means different tomato So we want two different alleles here. So capital R lowercase R We always put the capital first lowercase second. That's the genotype the way those two alleles can go together for a Red tomato that is going to be heterozygous now we're gonna do a Homozygous red All right, so if it's gonna be red it has to be a capital R And if it's homo meaning the same then it's got to be two capital Rs in a row Now we're gonna do a yellow tomato. There's only one way you can make a yellow tomato that's with the recessive gene and The recessive gene is the lowercase R. We're gonna have two of those together. So that would be your yellow tomato What's the phenotype of a tomato with two dominant alleles so if you had two dominant alleles We're gonna find the phenotype. Now phenotype is a fancy word for what does it actually look like? Like what does it present like? What does it physically look like? What could you see with your eyes? So two dominant alleles is gonna give you a red tomato What if you have one dominant and one recessive allele? All right So we did that earlier and that's also going to be red because that dominant capital R Allel is going to sort of win out over the recessive and make that red color appear Number two says in a certain flower the allele for yellow color Capital Y is dominant to the allele for orange color lowercase Y Determine the expected properties of the genotype and phenotype in offspring produced by the crosses between and we're gonna do three different examples So we're gonna start off here with a homozygous yellow and orange flowers and we're gonna figure out the probabilities of each All right, so let's figure out how to do this. We're gonna use a punnett square for this Punnett square is pretty easy to go and make we're gonna start off here by just putting down a little grid kind of like tic-tac-toe and We're gonna have spaces for the yellow flower So it says homozygous yellow. That means we're gonna have two capital Y is there All right, there's our yellow flower and the orange flower So if it's homozygous that means it's the same and to be orange you have that recessive gene Now we're gonna go and do the crosses Now the way we do these is we sort of just put the Y from above next to the Y on the left here Y from above next to the Y in the left just kind of combine the letters and fill in the results in the boxes and This one is actually not super interesting because as you can see every single one turns out exactly the same So that means that our our genotype Which means what is the Breakdown of all of your different letter combinations It's 100% the uppercase what Y lowercase Y for a phenotype same thing 100% Yellow that's what that uppercase Y lowercase Y means since the uppercase Y is telling us it's gonna be dominant for the yellow color Now we're gonna do two yellow flowers But they're gonna be heterozygous And we're gonna do ratios this time to show the breakdown of the phenotype and the genotype So here's one heterozygous yellow. Here's the other heterozygous yellow uppercase lowercase All right, so here's my first cross. I get two uppercase Y's All right, so that's gonna be one of the things that I'm gonna be able to talk about I've got an uppercase Y and a lowercase Y and another uppercase Y and a lowercase Y All right, so there was one of the double uppercase there are two of The uppercase lowercase and in the last box here, we have two Y's which are lowercase Okay to the recessives together Now for the ratios for the genotypes We had one out of four that were capital Y capital Y two out of four that were capital Y lowercase and one out of four that was lowercase lowercase Now let's take a look at the phenotype ratios. So these are going to be the ratios of the different colors We're going to see first. I need to work out what colors I have So I'm going to have capital Y capital Y that works out to be yellow two dominates together Capital lowercase. That's also a dominant there. So that's yellow and the two lowercase Y's are gonna bear oranges So we have three yellows compared to one orange You can write that as three to one if you're talking about the yellows or one to three if you're talking about the orange So last one here We're going to do an orange flower and a heterozygous yellow flower and we're going to do the probabilities as just a decimal and for percentage Sort of showing some different ways you can see these probabilities expressed Lowercase Y lowercase Y. So that's what our orange flower looks like The only way you can get oranges for those two recessives in this question and then uppercase Y lowercase Y For our heterozygous yellow do my crosses here Those two came out the same and then I've got two lower cases two lower cases All right, so for my genotype it looks like half of them so 0.5 as a probability as a decimal not a percentage will be lowercase Y uppercase Y and 0.5 of them will be lowercase Y lowercase Y for the phenotype Actually, what colors are going to be we're going to go and have kind of the same thing 0.5 percent chance or not percent chance probability chance of it being orange and same Chance of it being yellow Let's take a look at number six from our handout on the genetic practice Hand out. This is a sex-linked question. This one's a little bit different Then some of the punnett squares we looked at earlier, but the basic idea is the same All we're going to do differently now is we're going to deal with an X and a Y chromosome Instead of just an uppercase in a lowercase. So it's a little extra layer, but it's not too bad to do Number six says in one form of hemophilia a recessive X-linked allele Which is shown by X with a superscript H above it Increases blood clotting time That's what causes this disease and makes it so that it's hard for your blood to clot and leading to health issues Explain how hemophilic offspring can be born to two normal parents so in order to do this we need to make a punnett square and my punnett square is going to show the crosses between a man and a woman and Both of them are going to be normal, which means they won't have this particular disease Now, how do you know if someone has a disease or not in terms of writing down? All of these letters. So let's just start off by making a man and a woman So here's a woman to X chromosomes and here's a man an X and a Y chromosome Now it says this is a recessive X-linked allele So if it's a recessive sort of disease that means you only have it if you have two of those recessive recessive genes So we're not going to have anybody like that here because it says this question has is normal parents parents Who don't have the disease? So that means they might be carrying the disease, but they don't have two of the recessive alleles So I could have for the the mom here one of the recessive alleles lowercase H But also one of the dominant alleles now because she has that dominant allele. She won't actually have Hemophilia But she can still carry the gene for it and possibly pass it on to her children Now for the man here the Y doesn't get any H's on it because this is an X-linked disease All right, so we only have to really think about the X chromosomes, but certainly we will have a Letter on the X chromosome here, and I chose a capital H again because this is a normal parent This man here does not have hemophilia because he doesn't have that recessive allele So now let's go into our crosses so our crosses are going to contain the X's and the Y's as well as the H's so here's our first Possibility now this kid who I just drew out here will not have hemophilia the dominant capital H Will beat out the recessive lowercase H so that child would be a carrier for hemophilia, but wouldn't be effective And that would be a girl our next one here. We're going to have Let's put our Y first and then our X lowercase H So this person here Would have hemophilia all right because we've got no dominant capital H to beat out that lowercase H Just to finish it off really fast here Here's another possibility of a child this one isn't even a carrier for hemophilia So the disease sort of ends if this is the baby that's produced here with the two capital H's and our last one here And that was a girl Is a a Y and an X as well, but that X is again the dominant gene So those two children this boy this girl would not even be carriers of the diseases, but there is one possibility In fact, there's a one and four chance that The child is affected So you can see here how even if the parents don't necessarily have hemophilia They can be carriers of that recessive gene and possibly pass it off to the their child Letter B says can any of the female offspring? Inherent hemophilia no as we saw from our permits Punnett squares the two females we had here Females are made up of two X chromosomes Here's the first possibility that capital H The dominant not having hemophilia gene beats out the lowercase H so that child won't have it will be a carrier though The other woman That would be produced here has got too dominant for not having hemophilia So no chances that any females could inherit this disease