Assume you have mated a homozygous dominant purple, square pla...

Question

Assume you have mated a homozygous dominant purple, square plant with a homozygous recessive pink, spherical plant. What is the proportion of purple and spherical plants that would be produced in the F₂ generation?

Two Punnett squares illustrating a dihybrid cross for plant traits.

Accepted Answer

Okay. So in this question, we're gonna be doing a dihybrid cross with both the Punnett Square and the Branch method. So, so you can walk through whichever one you prefer or walk through both. I suggest you walk through both. So this question says, you made it a homozygous dominant purple square. So homozygous dominant for both with a homozygous recessive pink spherical plant. What's the proportion of the purple spherical plants that would be produced in the f 2 generation? So, first, my first thing that you have to know when you figure this out, what were you what were you given and what are you asked for? So in this case, they asked, they said that you have a homozygous dominant purple, so we'll say p p, and a homozygous dominant square. So we'll do, s s. And you made it that with a homozygous recessive pink, lowercase p's, spherical, lowercase s's. So this is your parental cross. Let me back out of the way already. So this is what you started with. Now, if you cross this, you're going to get an f one generation and that's fantastic, but what they're asking you for is the f two. And they're asking you, what's the proportion of purple spherical plants? So they're asking you for phenotypes, Purple spherical. Okay. So first, the very first thing we have to do is figure out the f one. Now the f one can be figured out. One, they're gonna be I'm just gonna give you the cheat to it. Gonna be heterozygous for all the traits. Now, how did I do that? How did I know that it was going to be p? It's gonna be these 2. Because if you take each one, let me get a different color. And cross it and you do that for each one, you're going to get uppercase p with lowercase p, uppercase p with lowercase p, uppercase s with lowercase s, uppercase s with lowercase s. And you're going to get that for every single thing that you do. Just 100%. It's what you're gonna get. So this is going to be your f one generation. Now, you are welcome to do a dihybrid cross to figure it out. But I suggest you just memorize the the short term. That anytime you cross a homozygous dominant with a homozygous recessive, you're going to get all heterozygous. I suggest you just memorize that. But if you forget or you're in a test and you're freaking out, feel free to do a Punnett square to figure it out. So now we have our f one and our f one is going to be what we put into the Punnett square. So remember how we do this? We take each trait individually. So we'll say this is the mother and this is the father. Let me scroll down. We're going to take each trait individually. So we start with a p, we have an uppercase p and a lowercase p, an uppercase p and a lowercase p. And we're gonna do that for the father as well. So that's what we start out with. Then we have our s's. So we're going to start out with the, uppercase s, lowercase s, but because this is the second trait, we do the opposite. Right? And that's just taking each combination that exists. So now that we have that, we can begin writing our traits. So this is, let me actually just use a completely different color. And I'm not going to do the colors like I did in the practice, but I'm just going to go through very quickly, and write this down. So, suggest you practice this a lot because you are going to get questions on it. And, you're gonna have to be able to do this in a test setting, Usually, you have limited time. So if you're not moving as fast as me right now, or you're not even close, you probably should put in some practice and make sure that you can actually do it this quickly. Because in a test setting, you may be given a lot of these and you're going to have to be able to do them quickly. Okay. So here's our offspring. Here's our dihybrid cross. How I did this is I took one from here, I took one from here, one from here, one from here. And I did that for every single box. Now, this is our offspring. So the question asked, what the proportion was would be a purple spherical plants. So purple, so anything with a p in it, so that could be pp or uppercase lowercase p is going to be purple. Spherical though is only going to be recessive. That's a recessive trait, which they gave us up here. Homozygous recessive pink spherical. So we know that the genotypes we're looking for are this in order to give us the phenotype that it asked for. So let's go through and figure out where those are. So there's lots of uppercase, p's and s's, but the first one that I see off the top of my head, is here. So let's keep going. Do you see any others? Yeah. There's one here with an upper case p, lowercase s's. And is there any more? Yeah. Here's one. And so, that is, 3 out of 16. So 3 out of 16, and that is your answer for this question. So that is the way to do it via Punnett Square. Now, let's try the Branching Method. So remember, we started off with our, homozygous dominant and recessive parents. Oops. Here we go. We know because of this little cheat that I told you that the f one generation is this, and it's asking us for the f 2. We're looking for either this or this. How many? So, the first thing you do is you take each tray individually. So, if you take each tray individually, what you get oh, see, I just got confused. So, with the parents, but we're starting with the f one because it's asking about the f two. So, if you tray each tray individually and do a monohybrid cross. Get 2 uppercase, 1 uppercase, 1 lowercase, uppercase lower, and 2 lower. So then, you have your purple. And, what what color was it? White? Is it white? Recessive pink. Pink. So out of this cross, 3 of the 4 are purple and one is pink. That's our first. Now, we have the next trait. And that's going to be, round and or what was it? I don't remember the traits. It was square and spherical. Let me go back and redo this. So square, cool. Square, spherical. Okay. So now, we have our second trait. So now, you can do your second cross, or if you just know it, which over time you'll just eventually get to know it. Essentially, we're working with uppercase and lowercase s's because we're dealing with the f one generation. So if I do this cross, what I get is the same proportion as I did with the color trait. So we have 3 that are square and one that is spherical. And so, you input those numbers here. So then, to get your traits here, you have purple, square, which we don't care about. Purple, spherical, which we do care about. So this is the one we're going to calculate. And how you do it, is you do 3 fourths, which was here, times 1 fourth, which is here, equals 3 16ths. So, your answer to this question would be 3 16th. That is how you do the branching diagram. Now, you would be given that question, and you could do it however you want. So I suggest you practice both methods and figure out, you know, do I like the Punnett Square method? Do I like the branch method? I personally prefer the branch method, but I like math. You're not good at math or you don't seem to if the this sort of product law doesn't really make sense to you, then go ahead do the Punnett square. If you get confused or get a number you don't think is right, the Punnett square is, you know, you can visualize it and see it. So that will always help. So, I realize these questions take forever. They're going to take forever on your test. So really practice them. Get your speed up with these Punnett Square, so that you know what you're doing, and can calculate these things quickly in a, like, test pressure situation.

Genetics 때문에 힘들어하고 계신가요?

Assume you have mated a homozygous dominant purple, square plant with a homozygous recessive pink, spherical plant. What is the proportion of purple and spherical plants that would be produced in the F₂ generation?

다음 시청

Dihybrid Cross 연습 세트

Genetics 때문에 힘들어하고 계신가요?

Assume you have mated a homozygous dominant purple, square plant with a homozygous recessive pink, spherical plant. What is the proportion of purple and spherical plants that would be produced in the F2 generation?

다음 시청

Dihybrid Cross 연습 세트

Assume you have mated a homozygous dominant purple, square plant with a homozygous recessive pink, spherical plant. What is the proportion of purple and spherical plants that would be produced in the F₂ generation?