Rikku of the Al Bhed (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
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fandomhigh2011-02-08 12:32 pm
the_merriest) wrote in fandomhigh2011-02-08 12:32 pm
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Science is Awesome!!!, Class #6, Period 3, February 8th
"This week, we're talking genetics," Rikku said. "Genetics is the study of genes. Genes are the way that information is passed down from your parents, and their parents, and it all gets expressed in you."
"That's not to get into a weird conversation about nature and nurture, or whether having crazy parents means you're going to end up crazy," she added, quickly. "We're talking about things like physical traits, mostly. I mean, you might be predisposed to certain things, but free will is pretty awesome, yeah?"
Said the cranky atheist, anyway.
"Let's talk about eyes. Although eyes are way more complicated than this, and this is a huge oversimplification, this is still a neat place to start, okay? Basically, a lot of times, you have two copies of something -- the one you got from your mom, and the one you got from your dad. Maybe your dad has brown eyes, and your mom has blue eyes, so you get a marker for brown and a marker for blue. How does that settle out? Well. Blue is what they call 'recessive,' which means if it's paired with brown, brown wins. Blue only gets expressed if it's with another marker for blue. So you'd end up having brown eyes, but you'd be a 'carrier' for blue."
She turned to the board and wrote "Bb" on it. "The big B is brown, since it's dominant, and the little b is for blue. So now! Let's say you meet someone, and they're a brown-eyed sweetie who's a carrier for blue, too."
Rikku was now drawing out a tic-tac-toe board on the chalkboard, and filling it in with various Bs and bs.
"Remember, you get one copy of anything from your mom, and one from your dad. Is it going to be the big-B, or the little-b? That's a fifty-fifty chance. So what does this square tell us?"
She pointed at the four spots, in turn. "This first square, with two capital Bs? This kid has brown eyes and isn't a carrier for blue at all. There are two kids with a capital-B and a small-b; those kids are gonna be brown-eyed carriers just like you and your honey. And then the last square is just little bs, which means the kid is gonna have blue eyes, even though neither of you do."
She smiled at everyone. "You probably won't have four kids that line up like that -- it's about probability. 50% chance of the same thing, another carrier for blue. 25% of brown with no carrier, and 25% of blue. If you're interested in what happens with different combinations -- like a non-carrier having kids with someone who is? You can draw out your own square and see the results. It's kind of neat."
"You might also be wondering why this matters. Who cares what color eyes your kids will have?" She shrugged. "We started with eyes because they're easy to understand. The same square works if we're talking about people who are healthy carriers for a horrible, crippling disease. There's a 25% chance their kid will have it. And if you follow that line of reasoning out? Then you'll see why it's such a bad idea for family members to breed, or for small populations not to pull outsiders in for generations and generations. Because when you have kids with someone just like you, then you have all the same weaknesses and recessive traits being expressed. There are some diseases that are uncommon in the population at large, but frequent in certain enclosed communities -- because so many people are carriers, now, and having kids with other carriers."
"One last thing. Genetics is complicated, and beyond that, there are always places where things branch off strangely -- genetic mutations, which can be bad, or good, or neither, just something that is. My people, we're a closed-off community, too, and we all have the same weird trait with our eyes: spiral pupils. When we have kids with outsiders, they don't have the pupils any more, which hints that it's recessive."
She set the chalk down and dusted her hands off. "If you want to pester me after class and take a peek at my eyes, that's totally fine by me. In the meantime, let's talk about genetics."
"That's not to get into a weird conversation about nature and nurture, or whether having crazy parents means you're going to end up crazy," she added, quickly. "We're talking about things like physical traits, mostly. I mean, you might be predisposed to certain things, but free will is pretty awesome, yeah?"
Said the cranky atheist, anyway.
"Let's talk about eyes. Although eyes are way more complicated than this, and this is a huge oversimplification, this is still a neat place to start, okay? Basically, a lot of times, you have two copies of something -- the one you got from your mom, and the one you got from your dad. Maybe your dad has brown eyes, and your mom has blue eyes, so you get a marker for brown and a marker for blue. How does that settle out? Well. Blue is what they call 'recessive,' which means if it's paired with brown, brown wins. Blue only gets expressed if it's with another marker for blue. So you'd end up having brown eyes, but you'd be a 'carrier' for blue."
She turned to the board and wrote "Bb" on it. "The big B is brown, since it's dominant, and the little b is for blue. So now! Let's say you meet someone, and they're a brown-eyed sweetie who's a carrier for blue, too."
Rikku was now drawing out a tic-tac-toe board on the chalkboard, and filling it in with various Bs and bs.
"Remember, you get one copy of anything from your mom, and one from your dad. Is it going to be the big-B, or the little-b? That's a fifty-fifty chance. So what does this square tell us?"
She pointed at the four spots, in turn. "This first square, with two capital Bs? This kid has brown eyes and isn't a carrier for blue at all. There are two kids with a capital-B and a small-b; those kids are gonna be brown-eyed carriers just like you and your honey. And then the last square is just little bs, which means the kid is gonna have blue eyes, even though neither of you do."
She smiled at everyone. "You probably won't have four kids that line up like that -- it's about probability. 50% chance of the same thing, another carrier for blue. 25% of brown with no carrier, and 25% of blue. If you're interested in what happens with different combinations -- like a non-carrier having kids with someone who is? You can draw out your own square and see the results. It's kind of neat."
"You might also be wondering why this matters. Who cares what color eyes your kids will have?" She shrugged. "We started with eyes because they're easy to understand. The same square works if we're talking about people who are healthy carriers for a horrible, crippling disease. There's a 25% chance their kid will have it. And if you follow that line of reasoning out? Then you'll see why it's such a bad idea for family members to breed, or for small populations not to pull outsiders in for generations and generations. Because when you have kids with someone just like you, then you have all the same weaknesses and recessive traits being expressed. There are some diseases that are uncommon in the population at large, but frequent in certain enclosed communities -- because so many people are carriers, now, and having kids with other carriers."
"One last thing. Genetics is complicated, and beyond that, there are always places where things branch off strangely -- genetic mutations, which can be bad, or good, or neither, just something that is. My people, we're a closed-off community, too, and we all have the same weird trait with our eyes: spiral pupils. When we have kids with outsiders, they don't have the pupils any more, which hints that it's recessive."
She set the chalk down and dusted her hands off. "If you want to pester me after class and take a peek at my eyes, that's totally fine by me. In the meantime, let's talk about genetics."
Re: Discussion - What You Inherited (And Not In the Fun Money Way) - SCI06