 Hi everyone, my name is Jessica and I'm a learning guide at Long Beach Public Library. Today we're going to be learning about Mendelian Punnett Squares. Have you signed up for summer reading yet? Make sure to do so at longbeach.beanstack.org and if you already have, make sure to plug in our code family under the activities tab to claim your prizes. Have you ever wondered why your hair is straight but your brother's sister's hair is curly or maybe why they have different colored eyes than you? Well, today we'll figure out how that happened with a Punnett square. But first, a few key words to help us get started. DNA. DNA is what makes you you. It's what determines how tall you're going to be, where your eye trailer is going to be and even if you can roll your tongue like a taco, like that. But now let's stay a little more specific. Alleles are a pod of your DNA that can determine what traits are shown. So there's different alleles for brown eyes, blue eyes and green eyes just like ice cream flavors. There's chocolate, vanilla, mint chocolate chip, but it's still ice cream. You'll get one allele from your mom and one allele from your dad. These can either be dominant or recessive. Now a dominant allele is what will have more of a say as to what's going on. Whereas a recessive allele, not so much unless it's paired with another recessive allele. If a recessive allele is paired with another recessive allele, you'll be stuck with a homozytous pairing. A homozytous pairing can be both dominant and recessive. That just means you have two of each. But if you have one of each, you'll be stuck with a heterozytous pairing. Now, those are a lot of big words. Let's put that into practice to see how much you've learned. Now, let's use my friend Sandra as an example. She has green eyes even though both her parents have brown eyes. How did that happen? We'll figure that out with a punnett square. Now to draw punnett squares, it's pretty easy. It's just a regular square with a line drawn down the middle from top to bottom and down the middle from left to right. So we're actually going to start with Sandra's grandparents. We'll do her mom's side first. It doesn't matter if you put male or female on either side, but typically male draws on top, female draws to the left. So let's say Sandra's grandfather on her mom's side has a homozytous pairing for brown eyes. That means he'll have a bid-by and a bid-by. Whereas her grandmother has a homozytous pairing for green eyes, which is a little b and a little b. So dominant alleles will have the capital letters and recessive alleles will have the lowercase letters, always. So let's pair them up. We'll typically draw from top to bottom and left to right just like how we drew our punnett square. So we'll pair our bid-by and a little b here. Same for the next square. We'll do our bid-by and a little b right here. And again top to bottom, bid-by and little b. And one more time with our bid-by and our little b. That's a lot of b's. Now what this shows us is that Sandra's mom had a 100% chance of having brown eyes thanks to that dominant b allele. Now this heterozytous pairing is going to follow to Sandra's example. But let's look at Sandra's dad's parents. Same thing. Her grandfather on top, her grandmother on the bottom. Now let's say both of Sandra's dad's parents have a heterozytous pairing for the brown-eyed allele. So bid-by, little b, bid-by, little b. Let's pair them up. We have our bid-by here from the top and a bid-by from the left. We'll have a bid-by here from over here and a little b from the top. Now the bid-by down here and the little b from right here. One more square to be left with little b and little b. So how many dominant alleles do we see? We see them in three of the squares. That means that Sandra's dad has a 75% chance of having brown eyes and only 25% chance of having green eyes thanks to the two excessive alleles. So let's say Sandra's parents both ended up with a heterozytous pairing of the brown-eyed alleles. So let's see what happened to Sandra. So now, looking at Sandra's parents' heterozytous pairs, let's see how Sandra came up. We'll put her dad on top with bid-by, little b, and her mom on the side with bid-by, little b. So now let's pair up her alleles. We will have a bid-by and a bid-by here. A bid-by and a little b here. A bid-by and a little b here. And just one last square with little b and little b here. So what does this tell us? It looks like Sandra had a 75% chance of having brown eyes thanks to that bid-by alleles. But she ended up with green eyes. She only had 25% chance of that happening to her. Pretty crazy. So now, I challenge you to make a punnett score at home to figure out how you ended up with the traits that you draw. You can do the same thing with curly hair or straight hair. Now here's a hint. Curly hair is dominant. So thank you for joining us, and maybe we'll see you next time. Bye.