Labradors can be three different colors.
lizcen/Getty Images/iStockphoto
Today we’re talking genes - the recipe for you!
We’ll go microscopic and check out how traits like hair color are passed down through your family. We’ll also hear the story of genetics pioneer Nettie Stevens and find out how current-day geneticist Janina Jeff (and host of the podcast In Those Genes) unlocks the information packed in genes.
And if you have ever wondered how two black Labrador retrievers can be the parents of a yellow Lab, you’re not alone. We have the answer to that too. All this and an especially rambunctious Mystery Sound.
Don’t forget to listen to through to the end, where the Moment of Um tackles the question: do we sneeze in our sleep?
Audio Transcript
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AUNDRA: You're listening to Brains On. We're serious about being curious.
CHILD 1: Brains On is supported in part by a grant from the National Science Foundation.
MOLLY BLOOM: OK, the studio is right over here.
AUNDRA: Oh, cool.
MOLLY BLOOM: But before we begin, we need to stand in front of Maisel, our full-length mirror on the studio door, do our power pose, and say, we got this.
AUNDRA: Wait. It looks like the mirror's already occupied.
MOLLY BLOOM: Bob?
BOB: Oh, hi, Molly. Oh, hi, Aundra.
AUNDRA: What are you looking at?
BOB: Yesterday, my aunt told me that I had my mom's eyebrows.
AUNDRA: OK.
BOB: But no. These are mine.
MOLLY BLOOM: I think she just meant your eyebrows look like your mom's eyebrows because you got half of your genes from her.
BOB: Oh, right. But these are my mom's jeans. I borrowed these pants from her, gosh, a few years ago now. But they're just so comfortable. I just keep forgetting to return them.
AUNDRA: No, Bob. Not J-E-A-N jeans, G-E-N-E genes. Mom genes, not mom jeans.
MOLLY BLOOM: Yeah, like the genetic material that provides the instructions to all the cells in your body.
BOB: Oh. Right. Of course.
[PHONE CHIMES]
Oh, hey, look. Mom's calling now. I'll put her on speaker. Hi, mom.
BOB AS MOM: Hello, dear. Are you going to come by after work today? I picked up some new popsicles at the store, and I was thinking of having them with chili for dinner.
BOB: Oh, I'll stop by for sure. I love chili pop night. And I'd love to take a look at your eyebrows, too.
BOB AS MOM: Oh, sure, honey. Well, we'll see you later.
BOB: Oh, what a great mom.
AUNDRA: Well, we have to head to the studio for taping. Have a good day, Bob.
MOLLY BLOOM: And you may want to consider stopping home before heading to your mom's. You don't want her to notice you've permanently borrowed her jeans.
BOB: Oh, right. I'll change into my jumpsuit. There' so many more pockets to stash my popsicle sticks.
MOLLY BLOOM: Sure. OK. Bye, Bob.
BOB: Bye. So if these eyebrows are my mom's, where did I get this nose?
MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and with me today is Aundra from Austin, Texas. Hi, Aundra.
AUNDRA: Hi, Molly.
MOLLY BLOOM: So you wrote to us saying that you would love for us to do an episode on genetics.
AUNDRA: Hello, my name is Aundra, and I am 10 years old. The reason why I want to learn more about genetics and DNA is because they're really cool and complicated.
Can someone scientifically explain what genetics and DNA do, and what's the difference between genetics and DNA? Also, how does DNA actually work? What does DNA look under a microscope? What does DNA stand for?
MOLLY BLOOM: And so do you say that you look more like your mom or your dad?
AUNDRA: My mom because she has brown curly hair.
MOLLY BLOOM: And you also have brown curly hair?
AUNDRA: Yeah.
MOLLY BLOOM: I do, too. But we're not related. Are there any traits that you're sure you got from your mom or you're sure you got from your dad?
AUNDRA: Probably both my parents' blue eyes.
MOLLY BLOOM: Hmm. Well, today, we are talking traits. And some traits have to do with the way that you look.
AUNDRA: Like your eye color-- blue, brown, green, or gray.
MOLLY BLOOM: Or your hair texture-- curly, kinky, wavy, straight.
AUNDRA: Other traits have to do with how your body works, like if you need glasses, or cilantro tastes like soap to you. Those are all traits, too.
MOLLY BLOOM: And your traits are inherited. That means you get them from your biological mother and father. They are passed down to you.
MARK: That's kind of like how my parents passed down this cool mouth harp to me.
[TWANGING]
I call it Mouthety Harpenstein, Musician and Adventurer.
[TWANGS]
MOLLY BLOOM: Hey, Mark. You may have inherited a mouth harp, but it's not a trait.
MARK: Oh, I know. Your traits come from your genes in your DNA, which lives in a chromosome that's packed in a cell. And you have millions and millions and millions of cells, and they make up everything in your body. And that's how it is. Can I get an oh, yeah?
AUNDRA: Oh, yeah.
MARK: My dude.
MOLLY BLOOM: Whoa, Mark, you just dropped a lot of knowledge there, maybe a little too much, too quick. Would you mind explaining that again?
MARK: Oh, I would love to, Molly. In fact, I prepared a little song on this very subject. Ready for the first verse?
MOLLY BLOOM: Oh, we're ready.
[TWANGS]
MARK: (SINGING) There once was a body made up of cells. Inside those cells, the chromosomes dwell. Do they like it there? Yes, they think it's swell.
Cells are these teeny tiny pieces of you, and of any living thing, really. We are each made up of trillions of cells. But they aren't all the same. Every cell is specialized to be and do different things. You have special hand cells in your hand, nose cells in your nose, brain cells in your brain, and pastrami in your stomach.
AUNDRA: You mean stomach cells in your stomach.
MARK: Oh, yeah. Those, too. So each cell has something called a nucleus. And in that nucleus, chromosomes. Chromosomes are these collections of string-like material, all squiggly, like spaghetti. So you ready for the next verse?
MOLLY BLOOM: Oh, yes.
MARK: OK.
[TWANGING]
(SINGING) There once was a body made up of cells. Inside those cells, the chromosomes dwell. Do they like it there? Well, they think it's swell.
The chromosomes are made up of DNA. What's that you say? Oh, just DNA. Its actual name is a mouthful to say. [CLEARS THROAT] So DNA stands for-- get ready-- deoxyribonucleic acid. Go ahead. Try saying it.
AUNDRA: Deoxyribonucleic acid.
MARK: Nice. But since we're pals with it, we can just call it DNA. And DNA is amazing. It's a super-long chain of molecules containing tons of information. In fact, it has all the information needed to make your body. It's like the entire recipe for you.
AUNDRA: Wow, that sounds important.
MARK: It is. And that's why it's inside almost every cell in your body. But like I mentioned before, your cells aren't all the same. So how do they know what kind of cell to be?
Well, the DNA has the instructions. One set of instructions is all about how to be hair-growing cell. Another set of instructions is about how to be a tongue cell or a toenail cell or whatever. We call these different sets of instructions genes, which leads me to the end of the song. Once more from the top, maestro.
[TWANGING]
(SINGING) There once was a body made up of cells. Inside those cells, the chromosomes dwell. Do they like it there? Well, they think it's swell.
And the chromosomes are made of DNA. What's that you say? Oh, just DNA. Its actual name is a mouthful to say.
MOLLY BLOOM: Deoxyribonucleic acid.
MARK: Very good. Now let's wrap this up. [INHALES DEEPLY] (SINGING) The DNA comes with sections called genes. They're instructions for stuff like eyeballs and spleens. They determine traits, or so it seems, like whether your eyes are (HARMONIZING) brown, blue, or green.
[APPLAUSE]
MOLLY BLOOM: Very well done, Mark.
MARK: Thank you, thank you.
AUNDRA: So cells have chromosomes, and chromosomes are made up of DNA, and DNA is broken into little sections called genes. That's a mouthful to say, but I think I got it.
MARK: Exactly. And it's those genes that determine your traits. So when someone says you inherited your eyes from your dad, what they mean is you have his eye genes. And also, in my case, what you have is a mouth harp.
[TWANGING]
[HORSE NEIGHS]
Come on, Mouthety Harpenstein. Let's set forth for our next adventure. Heeya!
MOLLY BLOOM: Wow, what an exit.
AUNDRA: Where did that horse come from, anyways?
MOLLY BLOOM: I have no idea. All right, so where were we? Oh, yeah, traits. They come from your genes. And you have a lot of genes, around 20,000 different ones.
AUNDRA: And as Mark mentioned, they are part of the DNA that's packed in your chromosomes.
MOLLY BLOOM: So here's where things get even more interesting. Your chromosomes, that genetic stuff dwelling in your cells, most people have 46 of them.
AUNDRA: Half of them-- so 23-- come from your biological dad.
MOLLY BLOOM: Thanks, bio dad. And the other half come from your biological mom. Thanks, bio mom.
AUNDRA: So that means we have chromosomes and DNA and genes from both of our biological parents. That's how we get traits like theirs.
MOLLY BLOOM: They've got their mom's eyes.
AUNDRA: He has his dad's ears.
MOLLY BLOOM: She definitely has her dad's nail beds. But even though all of our genes come from our parents' chromosomes, it doesn't mean you have all the same chromosomes that they do.
AUNDRA: Your parents have two sets of chromosomes, just like you.
MOLLY BLOOM: But before they pass those on to their child, something happens. The two sets of chromosomes from the biological mom get all shuffled around, sort of like a deck of cards. And then she passes down just one half of those shuffled-up chromosomes.
AUNDRA: The same thing happened with their bio dad's chromosomes.
MOLLY BLOOM: So the kid ends up with one set of chromosomes that's a mix of their dad's chromosomes and one set of chromosomes that's a mix of their mom's chromosomes.
AUNDRA: That's why we look like our parents, but still unique. It's sort of complicated and also awesome.
ROBOTIC VOICE: Brains brains brains on.
AUNDRA: OK. Aundra, before we go on, we're going to take a little break from talking, and do some listening instead.
[SOUND EFFECTS MEDLEY]
CHILD 2: (WHISPERING) Mystery sound.
MOLLY BLOOM: It's time for the mystery sound. Are you ready?
AUNDRA: Yes
MOLLY BLOOM: Here it is.
[HIGH-PITCHED WHIMPERING]
What do you think that might be?
AUNDRA: I think it's a puppy whimpering.
MOLLY BLOOM: Oh, very quick guess. Excellent guess. Well, we're going to hear it again and get the answer a little bit later in the show.
Right now, we're working on an episode all about spacesuits.
AUNDRA: You know, super cool and super functional outfits that let astronauts do stuff in the cold, dark void of space.
MOLLY BLOOM: Exactly. And that got us thinking, what if we could have cool super suits that let us do something right here on Earth? Aundra, what would your super suit do?
AUNDRA: Well, mine would probably be a marine animal suit that would let me become any marine animal and breathe underwater.
MOLLY BLOOM: Oh, that would be so cool. What marine animal do you have in mind?
AUNDRA: Probably a dolphin or a turtle.
MOLLY BLOOM: Well, listeners, we want to hear your super suit ideas, too, so please send them to us at brainson.org/contact. We'll include some of your answers in that space suit episode.
AUNDRA: And while you're there, you can send us mystery sounds, drawings, high fives, and questions, like this one.
LIBBY: Hi, my name is Libby, and I am eight years old. And I live in Nederland, Colorado. And my question is, do we sneeze when we are sleeping, but we just don't notice? Bye.
MOLLY BLOOM: We'll be back with the answer to that during our moment of um at the end of the show, and we'll read the latest group of names to be added to the Brains Honor Roll.
AUNDRA: And if you stick around to the very, very end, you'll hear the preview of the new episodes of Smash Boom Best.
MOLLY BLOOM: That's our debate show, where we use facts, lore, and the power of persuasion to convince you that one thing is cooler than another.
AUNDRA: This week, it's venom versus claws.
MOLLY BLOOM: It's a nail biter.
AUNDRA: So keep listening.
You're listening to Brains On from American Public Media. I'm Aundra.
MOLLY BLOOM: And I'm Molly. So we know a lot about genes and DNA and chromosomes. But a lot of what we know was learned relatively recently.
AUNDRA: Maybe you've heard people talk about XX and XY chromosomes.
MOLLY BLOOM: Those are the chromosomes that determine biological sex, like whether you're female or male. But how did we find out what those chromosomes did?
AUNDRA: Let's check back to the early 1900s, when lots of scientists were working to understand chromosomes and how parents pass traits on to kids.
MOLLY BLOOM: One of those scientists was a woman named Nettie Stevens.
MOLLY AS NETTIE STEVENS: The year was 1905. And I was looking really closely at chromosomes. I mean, literally. I was looking at these chromosomes with a microscope. I was interested in all kinds of insects, and I started with termites, sand crickets, cockroaches, mealworms, and aphids.
MEALWORM CELL: How do you do? How do you do? Mealworm cell here. So nice to finally have my time under the microscope spotlight.
MOLLY AS NETTIE STEVENS: [CHUCKLES] Don't mind the mealworm cells. They're an excitable bunch.
So we knew that parents made special cells to grow into kids. We knew these special cells contained a mix of genes from each of the parents. I wanted to know more about how parents pass on traits, and I ended up finding something pretty wild. I discovered how parents' cells give kids their biological sex. I counted the chromosomes in the cells from mealworm moms that become kids.
MEALWORM CELL: Meal worms rule!
MOLLY AS NETTIE STEVENS: Those cells are called eggs.
MEALWORM CELL: Way ahead of you, Nettie. Those eggs, they've got 10 chromosomes.
MOLLY AS NETTIE STEVENS: I also counted the chromosomes in the cells from mealworms dads that become kids, the sperm. Those cells have 10 chromosomes, too.
MEALWORM CELL: 10, 10, 10, 10, 10! It's the mealworm magic number.
MOLLY AS NETTIE STEVENS: And I did this a bunch of times. They all had 10 chromosomes. The chromosomes in the egg cells all looked pretty much the same, but in sperm cells, the 10th chromosome came in two sizes.
MEALWORM CELL: Hmm. This seems important.
MOLLY AS NETTIE STEVENS: Sometimes, the 10th chromosome in sperm cells was big, and sometimes, it was small. And what I noticed was that the male mealworms had those smaller 10th chromosomes, whereas female mealworms had bigger 10th chromosomes. So the 10th chromosome had to be the thing deciding mealworms' biological sex.
MEALWORM CELL: Wow! What a discovery! So happy I could help. On behalf of all the mealworm cells, I will gladly accept my Nobel Prize. Stockholm, here I come!
MOLLY AS NETTIE STEVENS: It was very exciting. And it turned out that what I saw under the microscope was true for lots of different animals, including humans. Biological dads give their kids the chromosome that decides their sex.
AUNDRA: Wow. Thanks, Nettie.
MOLLY AS NETTIE STEVENS: You're welcome.
MOLLY BLOOM: We've come a long way since scientists like Nettie first showed us what parents pass on to their kids. We have better tools now, too.
AUNDRA: Like machines that can read all the DNA in your chromosomes.
MOLLY BLOOM: Right. Those machines are helping scientists understand what all of our genes do and how they work.
AUNDRA: Janina Jeff is a geneticist. She works to understand all the information that's stored in our genes.
MOLLY BLOOM: All that information, the sequence of compounds that make up your DNA, is called your genome. And your genome makes you you. And Janina Jeff says even though all human genomes are over 99% the same, there's enough unique information that can reveal your history and the history of your ancestors.
JANINA JEFF: One of the things that we can do with studying the genome or all of those things, we can understand a story about your identity, or the recipe book that makes you you.
If you think about your DNA, you probably didn't realize that you have thousands of years of grandparents and great grandparents and relatives who you've never met, all within your DNA. But in order for us to understand who your ancestors are and who you are related to, we need to do some comparisons. We need to take your recipe book and see how similar your recipe book might be with other people.
All humans have a book of 300 pages. However, if, let's say, the book cover is different on my recipe book versus your recipe book, that might tell me something about your ancestors. That might say, well, my ancestors are from Africa, and your ancestors might be from Europe. And so that would be one thing. But we still have the same book because we're 99% the same. And so what I'm doing is looking for the book that is the most similar to you.
So if I say, OK, I compare your book to the library of books, and I say, well, Janina's book has a red cover and chapters 1 through 5 or X, Y, and Z. And that matches 20 of the books in our library. So we make an assumption that because there's a similarity in those books, or the genomes, that you are related.
As you can imagine, your book is-- it represents your individuality. So there is a point in the book where you won't have any matches to anything in the library. And what that describes is your true identity, what makes you you.
Or you might look in the library, and you say, oh, wow, of the 300 pages, you share 295 pages with someone else in the library. And it turns out, that's your mom or that's your dad.
African descendants have the oldest genomes. And that's because modern-day humans originated out of Africa. And as you can imagine, being the first, a lot of things can happen. Your ancestors have survived thousands of years of all these changes to keep you and the human population alive.
So African descendants, because they've been around for so long and because our ancestors were one of the first, have the most amount of variation, meaning, in those books, there are a lot of unique stories unique to African descendants.
MOLLY BLOOM: Janina Jeff says because there is so much variation in the books, or genomes, of people of African descent, there's a lot we can learn by reading those books. One thing she hopes to learn is how we can make better medicines and treatments that work well for everyone.
CHILDREN: Brains on!
Let's go back to that mystery sound. Here it is again.
[HIGH-PITCHED WHIMPERING]
Before, you thought maybe it was a puppy whimpering. Do you have new guesses, or you think you're going to stick with that one?
AUNDRA: I think I'm going to stick with that one. It's a very good guess, I think.
MOLLY BLOOM: Guess what? You are right. It is a puppy whimpering. Specifically, it's a Labrador Retriever named Marlow, a yellow one. Very cute. Do you have any dogs?
AUNDRA: Yes, I have one.
MOLLY BLOOM: What kind of dog?
AUNDRA: OK, we don't really know. We think it's a Dameranian, which is a Pomeranian and a Dachshund mixed.
MOLLY BLOOM: So what color is your dog?
AUNDRA: She's brown, tan, black, red, and white.
MOLLY BLOOM: Oh, my goodness. That's all the colors. And what's her name?
AUNDRA: Willa.
MOLLY BLOOM: Willa. Is she a good pup?
AUNDRA: Yes.
MOLLY BLOOM: So the reason that we're talking about Labrador puppies is that it's not just humans that have genes. Animals and plants do, too.
AUNDRA: And this listener has a very specific question about dogs.
MEGAN: My name is Megan. I'm from Windham, New Hampshire. I was wondering how we get our blonde hair or our brown eyes. My dog is a yellow Lab, and her parents are both black Labs. I know that they are genes, but how does that actually work?
MOLLY BLOOM: Excellent question, Megan. We asked Brains On producer, Menaka Wilhelm, to look into this.
MENAKA WILHELM: Ah. The puppy parent fur color mystery-- a classic. Are yellow Labs all secretly hitting the canine hair salon for fur touch-ups?
BOB AS DOG: [PANTING] Thank you so much for fitting me in. My roots were beginning to show.
MENAKA WILHELM: Nah, it's not canine hair colorists. It's dog genes, or genetics. The same way that our genes tell our cells what to do, dogs have genes, sections of DNA in their chromosomes, that boss their cells around, too. Take it from this dog cell.
DOG CELL: Oh, my. Oh, my. Oh, my. I am so happy to be making Labrador fur! This pup will be so warm and stylish.
[GASPS] Wait! Oh, no! Labs can have three colors of fur. There's brown, there's yellow, and black Labs. Oh! I need some instructions!
MENAKA WILHELM: Genes tell a dog's fur what color to be. And just like us, dogs have two sets of chromosomes. That's two versions of each gene.
[DRUMMING]
BOTH: We're two versions of a fur color gene. We tell you what color you can make.
DOG CELL: Oh, I am so glad you're here. So, which one of you do I listen to?
BOTH: You listen to both of us.
FUR COLOR GENE 1: I tell you instructions from one chromosome.
FUR COLOR GENE 2: And I tell you instructions from the other chromosome.
MENAKA WILHELM: But here's the thing about having these two versions of a gene. Your cells look at them both. But usually, one of the instructions will beat out the other version.
You know how rock always beats scissors in rock paper scissors? No matter what? It's a bit like that. But when genes only come in two flavors, one flavor of a gene just always wins over the other.
DOG CELL: OK. So what color do you all want me to make?
FUR COLOR GENE 1: Black.
FUR COLOR GENE 2: Brown.
FUR COLOR GENE 1: Rock beats scissors, and black beats brown. Ha!
FUR COLOR GENE 2: Fine.
DOG CELL: Great! So I'll make black.
MENAKA WILHELM: If both versions of that gene called for brown fur, then black wouldn't win out, brown would. And the dog's body would make brown-colored floof. That's how you get a brown Lab. Let's rewind and see.
BOTH: OK, your color will be--
FUR COLOR GENE 1: Brown.
FUR COLOR GENE 2: Brown.
DOG CELL: Brown it is.
FUR COLOR GENE 1: Is it really as fun if we agree?
FUR COLOR GENE 2: I just thought you'd say black again.
MENAKA WILHELM: But deciding black versus brown is only part of this process. There's more to this story.
DOG CELL: OK, I'm almost ready for my big reveal. Are you guys ready?
FUR COLOR GENE 1: Uh, yes, we're ready for this surprise. We decided what color you make, remember?
MENAKA WILHELM: Besides the versions of the gene we just met, there's another gene that helps decide a Labrador's color. Ta da! I'm yellow!
FUR COLOR GENE 2: Wait, what? I said brown.
FUR COLOR GENE 1: I said black. And black beats brown.
BOTH: Neither of us said anything about yellow.
BOTH: That's because we did.
FUR COLOR GENE 3: We decide if fur is a dark color, like black or brown, or if it's a light color, like yellow.
DOG CELL: Well, that's confusing. But you're the boss, boss-- bosses.
FUR COLOR GENE 4: Right. Brown or black might win over there between-- [CHUCKLES] --Gene Simmons and Jean Harlow. But if we pick light-colored fur, this puppy becomes a nice mellow yellow.
DOG CELL: Mm. Butter color.
MENAKA WILHELM: And for dark coloring versus light coloring, there's a version that always wins, too.
FUR COLOR GENE 3: In our case, dark coloring beats light coloring. But this time, we both agreed on light-colored fur.
BOTH: This will be a yellow Lab.
FUR COLOR GENE 1: This is unbelievable.
FUR COLOR GENE 2: Why are they doing this to us?
FUR COLOR GENE 1: What's going on?
FUR COLOR GENE 2: What are we supposed to do with this?
BOTH: We get the final say on the fur. Sorry.
DOG CELL: OK. I have a lot of fur to make. So I'll catch you guys later.
MENAKA WILHELM: Remember how this dog has both DNA for brown fur and DNA for black fur, even though it ended up being yellow? Those brown and black genes just got overruled by other genes. And that means that yellow Lab could pass down brown or black DNA to her kids and end up having black or brown puppies.
FUR COLOR GENE 1: No black fur this time. [SIGHS] But if I get passed on to a puppy, and I get paired with the right combination of genes, that puppy could be black.
MENAKA WILHELM: So that's how two black Labs can have a yellow Lab puppy, or two black dogs can have a yellow or a brown puppy. Even if it's not being expressed, a dog can still carry the gene for a different color fur in its DNA. And then it has potential to pass that gene down to its puppies.
AUNDRA: Wow. This is quite a system.
MENAKA WILHELM: I know. And for different dogs, there are different numbers and combinations of genes that decide colors and patterns, too. This is just for Labradors. Yeesh. In some ways, it would be simpler if the dogs just got their hair colored at a canine hair salon. Maybe I should look into that.
MOLLY BLOOM: It could be an interesting side hustle.
MENAKA WILHELM: I'll workshop and get back to you. Bye.
AUNDRA: Thank you. Bye.
MENAKA WILHELM: Bye.
MOLLY BLOOM: Your traits come from your genes--
AUNDRA: --which are sections of DNA--
MOLLY BLOOM: --which makes up your chromosomes--
AUNDRA: --and are in almost all your cells.
MOLLY BLOOM: Since you have two versions of the same gene--
AUNDRA: One from your bio mom and one from your bio dad.
MOLLY BLOOM: --sometimes, one version will override the other.
AUNDRA: So even if you have brown eyes, you might still have a gene for blue eyes somewhere in your DNA.
MOLLY BLOOM: And if you look at your whole genome and compare it to others, you can learn the story of your ancestors and what makes you you. That's it for this episode of Brains On.
AUNDRA: Brains On is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Our multitalented fellow is Menaka Wilhelm. And we had production help from Kristina Lopez and engineering help from Veronica Rodriguez, Cameron Wiley, and David Alvarez. Special thanks to Heena Srivastava, Shelly Langford, Rebekah Drumsta, Heather Norton, Jane Maienschein, Garland Allen, Rosie DuPont, Jim Bickel, Bill Lager, and Tracy Mumford.
AUNDRA: Brains On is a nonprofit public radio podcast. We rely on donations from our listeners to keep making new episodes.
MOLLY BLOOM: You can support the show and see our cool thank you gifts at brainson.org/donate.
AUNDRA: And before we go, it's time for a moment of um.
ALL: Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um.
CHILD 3: My question is, do we sneeze when we are sleeping, but we just don't notice?
MICHAEL HOWELL: Almost certainly not.
Achoo!
MICHAEL HOWELL: Hi, I'm Michael Howell. I'm a neurologist who is interested in sleep disorders at the University of Minnesota.
Sneezing is something that happens during the day, which helps clear out any noxious particles that gets up into our nose. So usually, first of all, we're not really walking around. We don't have a lot of air circulating through our nose when we're sleeping. We do a little bit, but not a lot.
In addition to that, when you fall asleep, your brain is less responsive to the environment. Certainly, we don't remember things. But if someone comes up and pinches you while you're asleep, you may very well not even notice it.
Same thing with these noxious feelings that can cause us to sneeze. Whether or not it's a little bit of pollen in our nose, or whether or not it's a little bit of dust, if those things circulate in through our nose when we're sleeping, it's very unlikely that our brain will trigger a sneeze, because it's just not-- our brain isn't receiving that noxious signal.
If someone were to wake up sneezing, I would, in fact, even say that probably indicates that you're not sleeping well, because it tells us that you're not-- your brain isn't getting deep enough asleep.
A couple of experiences that do frequently wake people up when they're sleeping, however, is coughing. So if they have a bad cold, if they have asthma, and they'll-- so to wake up coughing is not unusual. But that again, that also indicates that there's something wrong, which is we need to take care of the coughing and we need to help you get a better night of sleep.
CHILD 4: Um.
CHILD 5: Um.
CHILD 6: Um.
MOLLY BLOOM: Whether I'm wide awake or dreaming, these names are always on my mind. This is the Brains Honor Roll, the fantastic listeners who fuel our show with their terrific questions, ideas, mystery sounds, and drawings.
[LISTING HONOR ROLL]
ROBOTIC VOICE: (SINGING) Brains Honor Roll.
MOLLY BLOOM: We'll be back soon with more answers to your questions.
AUNDRA: Thanks for listening.
MOLLY BLOOM: And now for a sneak peek at this week's Smash Boom Best. It's venom versus claws. Which one is cooler? Well, this round kept our contestants, Brandi Brown and Tom Weber, in a state of puzzlement.
[QUIRKY MUSIC]
All right, Brandi, you're up first. Let's hear your acrostic poem about claws.
BRANDI BROWN: C-- can do all sorts of things. L-- less energy to use. A-- always there when you need them. W-- wounds because, sometimes, you're not trying to kill. S-- species don't evolve to tolerate claws.
MOLLY BLOOM: Mm. Very nice. Tom, let's hear your acrostic about venom.
TOM WEBER: All right, here we go. Venom-- V-- very toxic. E-- exacting. N-- not claws.
MOLLY BLOOM: [LAUGHS]
TOM WEBER: O-- offensive and defensive.
MOLLY BLOOM: Oh.
TOM WEBER: M-- medicine maker.
MOLLY BLOOM: Very nice work, both of you. Maddie, do you know who you want to give a point to for this sneak attack round?
MADDIE: I think I do.
MOLLY BLOOM: Oof. She decided quickly.
[BELL DINGS]
You can check out who wins this battle by subscribing to Smash Boom Best in your podcasting app. And after you listen, tell us who your favorite is. Cast a vote at smashboom.org.
[MUSIC PLAYING]
CHILD 1: Brains On is supported in part by a grant from the National Science Foundation.
MOLLY BLOOM: OK, the studio is right over here.
AUNDRA: Oh, cool.
MOLLY BLOOM: But before we begin, we need to stand in front of Maisel, our full-length mirror on the studio door, do our power pose, and say, we got this.
AUNDRA: Wait. It looks like the mirror's already occupied.
MOLLY BLOOM: Bob?
BOB: Oh, hi, Molly. Oh, hi, Aundra.
AUNDRA: What are you looking at?
BOB: Yesterday, my aunt told me that I had my mom's eyebrows.
AUNDRA: OK.
BOB: But no. These are mine.
MOLLY BLOOM: I think she just meant your eyebrows look like your mom's eyebrows because you got half of your genes from her.
BOB: Oh, right. But these are my mom's jeans. I borrowed these pants from her, gosh, a few years ago now. But they're just so comfortable. I just keep forgetting to return them.
AUNDRA: No, Bob. Not J-E-A-N jeans, G-E-N-E genes. Mom genes, not mom jeans.
MOLLY BLOOM: Yeah, like the genetic material that provides the instructions to all the cells in your body.
BOB: Oh. Right. Of course.
[PHONE CHIMES]
Oh, hey, look. Mom's calling now. I'll put her on speaker. Hi, mom.
BOB AS MOM: Hello, dear. Are you going to come by after work today? I picked up some new popsicles at the store, and I was thinking of having them with chili for dinner.
BOB: Oh, I'll stop by for sure. I love chili pop night. And I'd love to take a look at your eyebrows, too.
BOB AS MOM: Oh, sure, honey. Well, we'll see you later.
BOB: Oh, what a great mom.
AUNDRA: Well, we have to head to the studio for taping. Have a good day, Bob.
MOLLY BLOOM: And you may want to consider stopping home before heading to your mom's. You don't want her to notice you've permanently borrowed her jeans.
BOB: Oh, right. I'll change into my jumpsuit. There' so many more pockets to stash my popsicle sticks.
MOLLY BLOOM: Sure. OK. Bye, Bob.
BOB: Bye. So if these eyebrows are my mom's, where did I get this nose?
MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and with me today is Aundra from Austin, Texas. Hi, Aundra.
AUNDRA: Hi, Molly.
MOLLY BLOOM: So you wrote to us saying that you would love for us to do an episode on genetics.
AUNDRA: Hello, my name is Aundra, and I am 10 years old. The reason why I want to learn more about genetics and DNA is because they're really cool and complicated.
Can someone scientifically explain what genetics and DNA do, and what's the difference between genetics and DNA? Also, how does DNA actually work? What does DNA look under a microscope? What does DNA stand for?
MOLLY BLOOM: And so do you say that you look more like your mom or your dad?
AUNDRA: My mom because she has brown curly hair.
MOLLY BLOOM: And you also have brown curly hair?
AUNDRA: Yeah.
MOLLY BLOOM: I do, too. But we're not related. Are there any traits that you're sure you got from your mom or you're sure you got from your dad?
AUNDRA: Probably both my parents' blue eyes.
MOLLY BLOOM: Hmm. Well, today, we are talking traits. And some traits have to do with the way that you look.
AUNDRA: Like your eye color-- blue, brown, green, or gray.
MOLLY BLOOM: Or your hair texture-- curly, kinky, wavy, straight.
AUNDRA: Other traits have to do with how your body works, like if you need glasses, or cilantro tastes like soap to you. Those are all traits, too.
MOLLY BLOOM: And your traits are inherited. That means you get them from your biological mother and father. They are passed down to you.
MARK: That's kind of like how my parents passed down this cool mouth harp to me.
[TWANGING]
I call it Mouthety Harpenstein, Musician and Adventurer.
[TWANGS]
MOLLY BLOOM: Hey, Mark. You may have inherited a mouth harp, but it's not a trait.
MARK: Oh, I know. Your traits come from your genes in your DNA, which lives in a chromosome that's packed in a cell. And you have millions and millions and millions of cells, and they make up everything in your body. And that's how it is. Can I get an oh, yeah?
AUNDRA: Oh, yeah.
MARK: My dude.
MOLLY BLOOM: Whoa, Mark, you just dropped a lot of knowledge there, maybe a little too much, too quick. Would you mind explaining that again?
MARK: Oh, I would love to, Molly. In fact, I prepared a little song on this very subject. Ready for the first verse?
MOLLY BLOOM: Oh, we're ready.
[TWANGS]
MARK: (SINGING) There once was a body made up of cells. Inside those cells, the chromosomes dwell. Do they like it there? Yes, they think it's swell.
Cells are these teeny tiny pieces of you, and of any living thing, really. We are each made up of trillions of cells. But they aren't all the same. Every cell is specialized to be and do different things. You have special hand cells in your hand, nose cells in your nose, brain cells in your brain, and pastrami in your stomach.
AUNDRA: You mean stomach cells in your stomach.
MARK: Oh, yeah. Those, too. So each cell has something called a nucleus. And in that nucleus, chromosomes. Chromosomes are these collections of string-like material, all squiggly, like spaghetti. So you ready for the next verse?
MOLLY BLOOM: Oh, yes.
MARK: OK.
[TWANGING]
(SINGING) There once was a body made up of cells. Inside those cells, the chromosomes dwell. Do they like it there? Well, they think it's swell.
The chromosomes are made up of DNA. What's that you say? Oh, just DNA. Its actual name is a mouthful to say. [CLEARS THROAT] So DNA stands for-- get ready-- deoxyribonucleic acid. Go ahead. Try saying it.
AUNDRA: Deoxyribonucleic acid.
MARK: Nice. But since we're pals with it, we can just call it DNA. And DNA is amazing. It's a super-long chain of molecules containing tons of information. In fact, it has all the information needed to make your body. It's like the entire recipe for you.
AUNDRA: Wow, that sounds important.
MARK: It is. And that's why it's inside almost every cell in your body. But like I mentioned before, your cells aren't all the same. So how do they know what kind of cell to be?
Well, the DNA has the instructions. One set of instructions is all about how to be hair-growing cell. Another set of instructions is about how to be a tongue cell or a toenail cell or whatever. We call these different sets of instructions genes, which leads me to the end of the song. Once more from the top, maestro.
[TWANGING]
(SINGING) There once was a body made up of cells. Inside those cells, the chromosomes dwell. Do they like it there? Well, they think it's swell.
And the chromosomes are made of DNA. What's that you say? Oh, just DNA. Its actual name is a mouthful to say.
MOLLY BLOOM: Deoxyribonucleic acid.
MARK: Very good. Now let's wrap this up. [INHALES DEEPLY] (SINGING) The DNA comes with sections called genes. They're instructions for stuff like eyeballs and spleens. They determine traits, or so it seems, like whether your eyes are (HARMONIZING) brown, blue, or green.
[APPLAUSE]
MOLLY BLOOM: Very well done, Mark.
MARK: Thank you, thank you.
AUNDRA: So cells have chromosomes, and chromosomes are made up of DNA, and DNA is broken into little sections called genes. That's a mouthful to say, but I think I got it.
MARK: Exactly. And it's those genes that determine your traits. So when someone says you inherited your eyes from your dad, what they mean is you have his eye genes. And also, in my case, what you have is a mouth harp.
[TWANGING]
[HORSE NEIGHS]
Come on, Mouthety Harpenstein. Let's set forth for our next adventure. Heeya!
MOLLY BLOOM: Wow, what an exit.
AUNDRA: Where did that horse come from, anyways?
MOLLY BLOOM: I have no idea. All right, so where were we? Oh, yeah, traits. They come from your genes. And you have a lot of genes, around 20,000 different ones.
AUNDRA: And as Mark mentioned, they are part of the DNA that's packed in your chromosomes.
MOLLY BLOOM: So here's where things get even more interesting. Your chromosomes, that genetic stuff dwelling in your cells, most people have 46 of them.
AUNDRA: Half of them-- so 23-- come from your biological dad.
MOLLY BLOOM: Thanks, bio dad. And the other half come from your biological mom. Thanks, bio mom.
AUNDRA: So that means we have chromosomes and DNA and genes from both of our biological parents. That's how we get traits like theirs.
MOLLY BLOOM: They've got their mom's eyes.
AUNDRA: He has his dad's ears.
MOLLY BLOOM: She definitely has her dad's nail beds. But even though all of our genes come from our parents' chromosomes, it doesn't mean you have all the same chromosomes that they do.
AUNDRA: Your parents have two sets of chromosomes, just like you.
MOLLY BLOOM: But before they pass those on to their child, something happens. The two sets of chromosomes from the biological mom get all shuffled around, sort of like a deck of cards. And then she passes down just one half of those shuffled-up chromosomes.
AUNDRA: The same thing happened with their bio dad's chromosomes.
MOLLY BLOOM: So the kid ends up with one set of chromosomes that's a mix of their dad's chromosomes and one set of chromosomes that's a mix of their mom's chromosomes.
AUNDRA: That's why we look like our parents, but still unique. It's sort of complicated and also awesome.
ROBOTIC VOICE: Brains brains brains on.
AUNDRA: OK. Aundra, before we go on, we're going to take a little break from talking, and do some listening instead.
[SOUND EFFECTS MEDLEY]
CHILD 2: (WHISPERING) Mystery sound.
MOLLY BLOOM: It's time for the mystery sound. Are you ready?
AUNDRA: Yes
MOLLY BLOOM: Here it is.
[HIGH-PITCHED WHIMPERING]
What do you think that might be?
AUNDRA: I think it's a puppy whimpering.
MOLLY BLOOM: Oh, very quick guess. Excellent guess. Well, we're going to hear it again and get the answer a little bit later in the show.
Right now, we're working on an episode all about spacesuits.
AUNDRA: You know, super cool and super functional outfits that let astronauts do stuff in the cold, dark void of space.
MOLLY BLOOM: Exactly. And that got us thinking, what if we could have cool super suits that let us do something right here on Earth? Aundra, what would your super suit do?
AUNDRA: Well, mine would probably be a marine animal suit that would let me become any marine animal and breathe underwater.
MOLLY BLOOM: Oh, that would be so cool. What marine animal do you have in mind?
AUNDRA: Probably a dolphin or a turtle.
MOLLY BLOOM: Well, listeners, we want to hear your super suit ideas, too, so please send them to us at brainson.org/contact. We'll include some of your answers in that space suit episode.
AUNDRA: And while you're there, you can send us mystery sounds, drawings, high fives, and questions, like this one.
LIBBY: Hi, my name is Libby, and I am eight years old. And I live in Nederland, Colorado. And my question is, do we sneeze when we are sleeping, but we just don't notice? Bye.
MOLLY BLOOM: We'll be back with the answer to that during our moment of um at the end of the show, and we'll read the latest group of names to be added to the Brains Honor Roll.
AUNDRA: And if you stick around to the very, very end, you'll hear the preview of the new episodes of Smash Boom Best.
MOLLY BLOOM: That's our debate show, where we use facts, lore, and the power of persuasion to convince you that one thing is cooler than another.
AUNDRA: This week, it's venom versus claws.
MOLLY BLOOM: It's a nail biter.
AUNDRA: So keep listening.
You're listening to Brains On from American Public Media. I'm Aundra.
MOLLY BLOOM: And I'm Molly. So we know a lot about genes and DNA and chromosomes. But a lot of what we know was learned relatively recently.
AUNDRA: Maybe you've heard people talk about XX and XY chromosomes.
MOLLY BLOOM: Those are the chromosomes that determine biological sex, like whether you're female or male. But how did we find out what those chromosomes did?
AUNDRA: Let's check back to the early 1900s, when lots of scientists were working to understand chromosomes and how parents pass traits on to kids.
MOLLY BLOOM: One of those scientists was a woman named Nettie Stevens.
MOLLY AS NETTIE STEVENS: The year was 1905. And I was looking really closely at chromosomes. I mean, literally. I was looking at these chromosomes with a microscope. I was interested in all kinds of insects, and I started with termites, sand crickets, cockroaches, mealworms, and aphids.
MEALWORM CELL: How do you do? How do you do? Mealworm cell here. So nice to finally have my time under the microscope spotlight.
MOLLY AS NETTIE STEVENS: [CHUCKLES] Don't mind the mealworm cells. They're an excitable bunch.
So we knew that parents made special cells to grow into kids. We knew these special cells contained a mix of genes from each of the parents. I wanted to know more about how parents pass on traits, and I ended up finding something pretty wild. I discovered how parents' cells give kids their biological sex. I counted the chromosomes in the cells from mealworm moms that become kids.
MEALWORM CELL: Meal worms rule!
MOLLY AS NETTIE STEVENS: Those cells are called eggs.
MEALWORM CELL: Way ahead of you, Nettie. Those eggs, they've got 10 chromosomes.
MOLLY AS NETTIE STEVENS: I also counted the chromosomes in the cells from mealworms dads that become kids, the sperm. Those cells have 10 chromosomes, too.
MEALWORM CELL: 10, 10, 10, 10, 10! It's the mealworm magic number.
MOLLY AS NETTIE STEVENS: And I did this a bunch of times. They all had 10 chromosomes. The chromosomes in the egg cells all looked pretty much the same, but in sperm cells, the 10th chromosome came in two sizes.
MEALWORM CELL: Hmm. This seems important.
MOLLY AS NETTIE STEVENS: Sometimes, the 10th chromosome in sperm cells was big, and sometimes, it was small. And what I noticed was that the male mealworms had those smaller 10th chromosomes, whereas female mealworms had bigger 10th chromosomes. So the 10th chromosome had to be the thing deciding mealworms' biological sex.
MEALWORM CELL: Wow! What a discovery! So happy I could help. On behalf of all the mealworm cells, I will gladly accept my Nobel Prize. Stockholm, here I come!
MOLLY AS NETTIE STEVENS: It was very exciting. And it turned out that what I saw under the microscope was true for lots of different animals, including humans. Biological dads give their kids the chromosome that decides their sex.
AUNDRA: Wow. Thanks, Nettie.
MOLLY AS NETTIE STEVENS: You're welcome.
MOLLY BLOOM: We've come a long way since scientists like Nettie first showed us what parents pass on to their kids. We have better tools now, too.
AUNDRA: Like machines that can read all the DNA in your chromosomes.
MOLLY BLOOM: Right. Those machines are helping scientists understand what all of our genes do and how they work.
AUNDRA: Janina Jeff is a geneticist. She works to understand all the information that's stored in our genes.
MOLLY BLOOM: All that information, the sequence of compounds that make up your DNA, is called your genome. And your genome makes you you. And Janina Jeff says even though all human genomes are over 99% the same, there's enough unique information that can reveal your history and the history of your ancestors.
JANINA JEFF: One of the things that we can do with studying the genome or all of those things, we can understand a story about your identity, or the recipe book that makes you you.
If you think about your DNA, you probably didn't realize that you have thousands of years of grandparents and great grandparents and relatives who you've never met, all within your DNA. But in order for us to understand who your ancestors are and who you are related to, we need to do some comparisons. We need to take your recipe book and see how similar your recipe book might be with other people.
All humans have a book of 300 pages. However, if, let's say, the book cover is different on my recipe book versus your recipe book, that might tell me something about your ancestors. That might say, well, my ancestors are from Africa, and your ancestors might be from Europe. And so that would be one thing. But we still have the same book because we're 99% the same. And so what I'm doing is looking for the book that is the most similar to you.
So if I say, OK, I compare your book to the library of books, and I say, well, Janina's book has a red cover and chapters 1 through 5 or X, Y, and Z. And that matches 20 of the books in our library. So we make an assumption that because there's a similarity in those books, or the genomes, that you are related.
As you can imagine, your book is-- it represents your individuality. So there is a point in the book where you won't have any matches to anything in the library. And what that describes is your true identity, what makes you you.
Or you might look in the library, and you say, oh, wow, of the 300 pages, you share 295 pages with someone else in the library. And it turns out, that's your mom or that's your dad.
African descendants have the oldest genomes. And that's because modern-day humans originated out of Africa. And as you can imagine, being the first, a lot of things can happen. Your ancestors have survived thousands of years of all these changes to keep you and the human population alive.
So African descendants, because they've been around for so long and because our ancestors were one of the first, have the most amount of variation, meaning, in those books, there are a lot of unique stories unique to African descendants.
MOLLY BLOOM: Janina Jeff says because there is so much variation in the books, or genomes, of people of African descent, there's a lot we can learn by reading those books. One thing she hopes to learn is how we can make better medicines and treatments that work well for everyone.
CHILDREN: Brains on!
Let's go back to that mystery sound. Here it is again.
[HIGH-PITCHED WHIMPERING]
Before, you thought maybe it was a puppy whimpering. Do you have new guesses, or you think you're going to stick with that one?
AUNDRA: I think I'm going to stick with that one. It's a very good guess, I think.
MOLLY BLOOM: Guess what? You are right. It is a puppy whimpering. Specifically, it's a Labrador Retriever named Marlow, a yellow one. Very cute. Do you have any dogs?
AUNDRA: Yes, I have one.
MOLLY BLOOM: What kind of dog?
AUNDRA: OK, we don't really know. We think it's a Dameranian, which is a Pomeranian and a Dachshund mixed.
MOLLY BLOOM: So what color is your dog?
AUNDRA: She's brown, tan, black, red, and white.
MOLLY BLOOM: Oh, my goodness. That's all the colors. And what's her name?
AUNDRA: Willa.
MOLLY BLOOM: Willa. Is she a good pup?
AUNDRA: Yes.
MOLLY BLOOM: So the reason that we're talking about Labrador puppies is that it's not just humans that have genes. Animals and plants do, too.
AUNDRA: And this listener has a very specific question about dogs.
MEGAN: My name is Megan. I'm from Windham, New Hampshire. I was wondering how we get our blonde hair or our brown eyes. My dog is a yellow Lab, and her parents are both black Labs. I know that they are genes, but how does that actually work?
MOLLY BLOOM: Excellent question, Megan. We asked Brains On producer, Menaka Wilhelm, to look into this.
MENAKA WILHELM: Ah. The puppy parent fur color mystery-- a classic. Are yellow Labs all secretly hitting the canine hair salon for fur touch-ups?
BOB AS DOG: [PANTING] Thank you so much for fitting me in. My roots were beginning to show.
MENAKA WILHELM: Nah, it's not canine hair colorists. It's dog genes, or genetics. The same way that our genes tell our cells what to do, dogs have genes, sections of DNA in their chromosomes, that boss their cells around, too. Take it from this dog cell.
DOG CELL: Oh, my. Oh, my. Oh, my. I am so happy to be making Labrador fur! This pup will be so warm and stylish.
[GASPS] Wait! Oh, no! Labs can have three colors of fur. There's brown, there's yellow, and black Labs. Oh! I need some instructions!
MENAKA WILHELM: Genes tell a dog's fur what color to be. And just like us, dogs have two sets of chromosomes. That's two versions of each gene.
[DRUMMING]
BOTH: We're two versions of a fur color gene. We tell you what color you can make.
DOG CELL: Oh, I am so glad you're here. So, which one of you do I listen to?
BOTH: You listen to both of us.
FUR COLOR GENE 1: I tell you instructions from one chromosome.
FUR COLOR GENE 2: And I tell you instructions from the other chromosome.
MENAKA WILHELM: But here's the thing about having these two versions of a gene. Your cells look at them both. But usually, one of the instructions will beat out the other version.
You know how rock always beats scissors in rock paper scissors? No matter what? It's a bit like that. But when genes only come in two flavors, one flavor of a gene just always wins over the other.
DOG CELL: OK. So what color do you all want me to make?
FUR COLOR GENE 1: Black.
FUR COLOR GENE 2: Brown.
FUR COLOR GENE 1: Rock beats scissors, and black beats brown. Ha!
FUR COLOR GENE 2: Fine.
DOG CELL: Great! So I'll make black.
MENAKA WILHELM: If both versions of that gene called for brown fur, then black wouldn't win out, brown would. And the dog's body would make brown-colored floof. That's how you get a brown Lab. Let's rewind and see.
BOTH: OK, your color will be--
FUR COLOR GENE 1: Brown.
FUR COLOR GENE 2: Brown.
DOG CELL: Brown it is.
FUR COLOR GENE 1: Is it really as fun if we agree?
FUR COLOR GENE 2: I just thought you'd say black again.
MENAKA WILHELM: But deciding black versus brown is only part of this process. There's more to this story.
DOG CELL: OK, I'm almost ready for my big reveal. Are you guys ready?
FUR COLOR GENE 1: Uh, yes, we're ready for this surprise. We decided what color you make, remember?
MENAKA WILHELM: Besides the versions of the gene we just met, there's another gene that helps decide a Labrador's color. Ta da! I'm yellow!
FUR COLOR GENE 2: Wait, what? I said brown.
FUR COLOR GENE 1: I said black. And black beats brown.
BOTH: Neither of us said anything about yellow.
BOTH: That's because we did.
FUR COLOR GENE 3: We decide if fur is a dark color, like black or brown, or if it's a light color, like yellow.
DOG CELL: Well, that's confusing. But you're the boss, boss-- bosses.
FUR COLOR GENE 4: Right. Brown or black might win over there between-- [CHUCKLES] --Gene Simmons and Jean Harlow. But if we pick light-colored fur, this puppy becomes a nice mellow yellow.
DOG CELL: Mm. Butter color.
MENAKA WILHELM: And for dark coloring versus light coloring, there's a version that always wins, too.
FUR COLOR GENE 3: In our case, dark coloring beats light coloring. But this time, we both agreed on light-colored fur.
BOTH: This will be a yellow Lab.
FUR COLOR GENE 1: This is unbelievable.
FUR COLOR GENE 2: Why are they doing this to us?
FUR COLOR GENE 1: What's going on?
FUR COLOR GENE 2: What are we supposed to do with this?
BOTH: We get the final say on the fur. Sorry.
DOG CELL: OK. I have a lot of fur to make. So I'll catch you guys later.
MENAKA WILHELM: Remember how this dog has both DNA for brown fur and DNA for black fur, even though it ended up being yellow? Those brown and black genes just got overruled by other genes. And that means that yellow Lab could pass down brown or black DNA to her kids and end up having black or brown puppies.
FUR COLOR GENE 1: No black fur this time. [SIGHS] But if I get passed on to a puppy, and I get paired with the right combination of genes, that puppy could be black.
MENAKA WILHELM: So that's how two black Labs can have a yellow Lab puppy, or two black dogs can have a yellow or a brown puppy. Even if it's not being expressed, a dog can still carry the gene for a different color fur in its DNA. And then it has potential to pass that gene down to its puppies.
AUNDRA: Wow. This is quite a system.
MENAKA WILHELM: I know. And for different dogs, there are different numbers and combinations of genes that decide colors and patterns, too. This is just for Labradors. Yeesh. In some ways, it would be simpler if the dogs just got their hair colored at a canine hair salon. Maybe I should look into that.
MOLLY BLOOM: It could be an interesting side hustle.
MENAKA WILHELM: I'll workshop and get back to you. Bye.
AUNDRA: Thank you. Bye.
MENAKA WILHELM: Bye.
MOLLY BLOOM: Your traits come from your genes--
AUNDRA: --which are sections of DNA--
MOLLY BLOOM: --which makes up your chromosomes--
AUNDRA: --and are in almost all your cells.
MOLLY BLOOM: Since you have two versions of the same gene--
AUNDRA: One from your bio mom and one from your bio dad.
MOLLY BLOOM: --sometimes, one version will override the other.
AUNDRA: So even if you have brown eyes, you might still have a gene for blue eyes somewhere in your DNA.
MOLLY BLOOM: And if you look at your whole genome and compare it to others, you can learn the story of your ancestors and what makes you you. That's it for this episode of Brains On.
AUNDRA: Brains On is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Our multitalented fellow is Menaka Wilhelm. And we had production help from Kristina Lopez and engineering help from Veronica Rodriguez, Cameron Wiley, and David Alvarez. Special thanks to Heena Srivastava, Shelly Langford, Rebekah Drumsta, Heather Norton, Jane Maienschein, Garland Allen, Rosie DuPont, Jim Bickel, Bill Lager, and Tracy Mumford.
AUNDRA: Brains On is a nonprofit public radio podcast. We rely on donations from our listeners to keep making new episodes.
MOLLY BLOOM: You can support the show and see our cool thank you gifts at brainson.org/donate.
AUNDRA: And before we go, it's time for a moment of um.
ALL: Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um. Um.
CHILD 3: My question is, do we sneeze when we are sleeping, but we just don't notice?
MICHAEL HOWELL: Almost certainly not.
Achoo!
MICHAEL HOWELL: Hi, I'm Michael Howell. I'm a neurologist who is interested in sleep disorders at the University of Minnesota.
Sneezing is something that happens during the day, which helps clear out any noxious particles that gets up into our nose. So usually, first of all, we're not really walking around. We don't have a lot of air circulating through our nose when we're sleeping. We do a little bit, but not a lot.
In addition to that, when you fall asleep, your brain is less responsive to the environment. Certainly, we don't remember things. But if someone comes up and pinches you while you're asleep, you may very well not even notice it.
Same thing with these noxious feelings that can cause us to sneeze. Whether or not it's a little bit of pollen in our nose, or whether or not it's a little bit of dust, if those things circulate in through our nose when we're sleeping, it's very unlikely that our brain will trigger a sneeze, because it's just not-- our brain isn't receiving that noxious signal.
If someone were to wake up sneezing, I would, in fact, even say that probably indicates that you're not sleeping well, because it tells us that you're not-- your brain isn't getting deep enough asleep.
A couple of experiences that do frequently wake people up when they're sleeping, however, is coughing. So if they have a bad cold, if they have asthma, and they'll-- so to wake up coughing is not unusual. But that again, that also indicates that there's something wrong, which is we need to take care of the coughing and we need to help you get a better night of sleep.
CHILD 4: Um.
CHILD 5: Um.
CHILD 6: Um.
MOLLY BLOOM: Whether I'm wide awake or dreaming, these names are always on my mind. This is the Brains Honor Roll, the fantastic listeners who fuel our show with their terrific questions, ideas, mystery sounds, and drawings.
[LISTING HONOR ROLL]
ROBOTIC VOICE: (SINGING) Brains Honor Roll.
MOLLY BLOOM: We'll be back soon with more answers to your questions.
AUNDRA: Thanks for listening.
MOLLY BLOOM: And now for a sneak peek at this week's Smash Boom Best. It's venom versus claws. Which one is cooler? Well, this round kept our contestants, Brandi Brown and Tom Weber, in a state of puzzlement.
[QUIRKY MUSIC]
All right, Brandi, you're up first. Let's hear your acrostic poem about claws.
BRANDI BROWN: C-- can do all sorts of things. L-- less energy to use. A-- always there when you need them. W-- wounds because, sometimes, you're not trying to kill. S-- species don't evolve to tolerate claws.
MOLLY BLOOM: Mm. Very nice. Tom, let's hear your acrostic about venom.
TOM WEBER: All right, here we go. Venom-- V-- very toxic. E-- exacting. N-- not claws.
MOLLY BLOOM: [LAUGHS]
TOM WEBER: O-- offensive and defensive.
MOLLY BLOOM: Oh.
TOM WEBER: M-- medicine maker.
MOLLY BLOOM: Very nice work, both of you. Maddie, do you know who you want to give a point to for this sneak attack round?
MADDIE: I think I do.
MOLLY BLOOM: Oof. She decided quickly.
[BELL DINGS]
You can check out who wins this battle by subscribing to Smash Boom Best in your podcasting app. And after you listen, tell us who your favorite is. Cast a vote at smashboom.org.
[MUSIC PLAYING]
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