MS. REBECCA ROBERTSFrom WAMU 88.5 at American University in Washington welcome to "The Kojo Nnamdi Show," connecting your community with the world. I'm Rebecca Roberts sitting in for Kojo. Your body carries enough DNA to stretch from Pluto to the Sun.

MS. REBECCA ROBERTSEach cell in your body has over six feet of it. And those seemingly endless chains of the letters A and C and T and G contain entire universes of clues about who we are and who we've been.

MS. REBECCA ROBERTSAt its core, DNA is the language used to write the story of our genes. A simple four-letter alphabet that can pave the way for everything from Elizabeth Taylor's trademark double eye lashes to the quirkiness of cat hoarders.

MS. REBECCA ROBERTSDNA allows us to look backward and has left clues about whether the human race came perilously close to extinction. And DNA science of course allows us to see into our individual futures. And new information is being discovered all the time.

MS. REBECCA ROBERTSJoining me here to talk about what our DNA can tell us about ourselves and our history is Sam Kean. His latest book is called "The Violinist's Thumb: And Other Lost Tales of Love, War, and Genius, as Written by our Genetic Code." Sam Kean, welcome to "The Kojo Nnamdi Show."

MR. SAM KEANHello, thanks for having me.

ROBERTSI have to start by asking about the title of the book. Why "The Violinist's Thumb" and what does that have to do with genetic history?

KEANAh, sure. "The Violinist's Thumb" has to do with one of the stories in the book about the violinist Niccolo Paganini. He's usually considered the greatest violinist who ever lived. He was active in Europe in the early 1800s. He was playing for popes and emperors. Napoleon had him at one point. And there were always rumors that he had sold his soul to Satan for his talent.

ROBERTSThere were a lot of rumors about him. He sounded like a pretty difficult guy.

KEANYes, some more realistic than others, but yes, lots of rumors. And part of the reason he was so good was he had these incredibly, kind of freakishly flexible fingers. He could twist them into all sorts of different positions.

KEANHe could spread his hands incredibly wide. He could just do things with his hands that lesser violinists could not do. And from a modern perspective it's almost certain that Paganini had a genetic disorder of some sort because not only were his hands extremely flexible, all of his joints were very, very flexible.

KEANWhen he was standing on stage his hips would be cocked at weird angles. His knees would be almost bending backwards. He was just sort of, kind of circus-ly, freakishly flexible in that way.

KEANAnd I chose the story as the title story for a couple of reasons. In addition to his hands, Paganini was also a very, very hard worker and he also had a deep passion for music. So it was not only his genetic endowment, it was his genetic endowment working with his temperament and his environment to really make him who he was. And that's one of the themes I stressed throughout the book is that it's your environment and genes working together to make you who you are.

KEANThe other reason I chose it is that it's just a good example of the kind of stories that are in the book, a lot of historical stories and things that can kind of shed light on mysteries in the past. A lot of details that we thought might be lost because they happened too long ago we can finally kind of read these stories in our DNA for the very first time, so...

ROBERTSWell, the other reason I like the story is because it sort of shows the double-edge sword nature of a lot of these genetic differences, is that while giving him this extraordinary gift of being able to move his fingers in a certain way, it was also a pretty serious health problem.

KEANYeah, he ended up with a lot of health problems and the last few years of his life, he couldn't even play in public because he had so many problems. And he ended up dying fairly young, much younger than he probably should have if he hadn't had this genetic disorder. So while it helped make him on the one hand, it kind of unmade him on the other hand, in the end.

ROBERTSSo we've used the term genetic disorder. Let's define our terms a little bit. What are we talking about when we talk about a gene and what can go wrong with a gene?

KEANYeah, the way I like to think about the distinction between genes and DNA, DNA is a chemical. It's a thing that you can get stuck to your fingers. And it has a roll inside the cell to store information so you can pass it to the next generation. So in a lot of ways DNA works like a language.

KEANAnd if DNA is a language, then genes are like a story with DNA as the language that the story is written in. So genes are a little more, I guess conceptual, a little more abstract. And you can talk about genes sometimes without even knowing that DNA was involved which scientists did for a very long time in their history.

KEANAnd if you want to talk about more a physical basis of genes, basically it's just a stretch of DNA that usually makes a protein is how we traditionally think of it.

ROBERTSOr makes RNA, which makes the protein?

KEANIt makes, yeah, right, it makes RNA which makes the protein.

ROBERTSBefore we get every biochemist on the line telling us DNA does not make proteins. But there's plenty of DNA that is not part of genes.

KEANYeah, if you look at the part of our DNA that eventually makes proteins, that only makes up about 2 percent, or even a little less of our DNA. So 98 percent of it doesn't do what we traditionally think about in terms of genes. And for a long time, scientists really didn't have any idea, good idea, what it was.

KEANSome of it actually is old, broken down virus DNA, 8 percent or so, so you know, by that measure, at least we're four times more virus than we are human and a lot of the rest of it we just didn't know what it did. And at some point, it got labeled as junk DNA. It's kind of a pejorative term that a lot of scientists, I think, regret nowadays because they know, in fact, that it's not junk, that it does have a role in the body, just a different role than they might have thought.

ROBERTSWell, I noticed you were careful to call it non-coding DNA.

KEANIn the book, yes, that's what a scientist would call it nowadays, non-coding DNA.

ROBERTSAnd actually there have been some new announcements about what some of that non-coding DNA might do just in the last week. There's this huge, international consortium of people studying the DNA outside of the genetic material and it seems to have a role in switching genes on and off?

KEANYeah it plays a regulatory role, a lot of it and exactly like you said, it turns genes on and off. It can turn the volume up and down on genes. It just kind of tweaks genes and it can do little things differently with genes than we might have thought about with traditional just regular, old genetics.

KEANAnd it helps explain things like, why even though all of the different cells in our body have the same DNA, obviously they work very, very differently. Your liver cells, your brain cells, skin cells, all of them look very different despite having the same DNA.

KEANOne reason why is, they're turning genes, different genes, on and off inside you so I think this project is really, really exciting. I really think you can go a long way toward figuring out what all the rest of that DNA does.

ROBERTSWell, the other thing, to me it helped explain was, when you hear something like we share 98 percent of our DNA with chimpanzees, you think, wow. Well, that 2 percent accounts for a lot. I mean, it's given us language and, you know, less body hair and bipedal walking and wow. That's a serious 2 percent.

ROBERTSBut if you understand that, yes, we have the same genetic material. But it turned off and on at different times and it, you know, some of it in proportion to others is extended throughout our lifetime in different ways than it is in the chimpanzee. Then you realize, okay, same blueprint, but different execution of the plans.

KEANYeah, and chimpanzees do regulate their DNA in a much different way than human beings do. Human beings, for instance, especially in our neurons, we're very good about, say, splicing DNA. So you take the same DNA, but you mix it up a little bit. You include different segments of DNA and different types of cells, things like that.

KEANSo in terms of defining what really makes us human on a DNA level, it might not be so much what we have as what we do with what we have. That might be the really big thing that makes us different on that level.

ROBERTSIn the book, you go into detail about the human genome project this public, private rivalry and the outsize characters involved and they all seem to have, you know, made enemies as well as friends and the race as it kind of became between Celera and Craig Ventor and the public consortium.

ROBERTSAnd then, sort of with hindsight a couple of years on, you make the point that, you know, it wasn't all just to win the race. It was supposed to then lead to more understanding of human disease and that that promise hasn't really been fulfilled that much.

ROBERTSBut reading the news this week about the non-coding DNA, it started to make some connections, in my mind at least, that maybe genes aren't the place to look for where it goes wrong, where something goes wrong.

ROBERTSMaybe if you're looking at that genetic map to figure out how humans get disease and therefore how to treat them, it's actually the switches you should be looking at.

KEANYeah, that is a good point and you can see a lot of the scientists when they were talking about this new project, they did. They were trying to temper expectations, in some cases, by saying, you know, we've learned the hard way before that it's not just that we find the information, we automatically get cures to diseases.

KEANBut this is a promising avenue for figuring out some of the other things that could go into causing diseases in people because as you said if you just look at the DNA inside genes it can't always explain everything that we know about diseases and how they get inherited. So we have to look elsewhere and this is a very promising lead for the other places to start looking.

KEANIt doesn't necessarily mean it will quickly translate into medical cures, but at least we know a little bit, a better place where to look now.

ROBERTSWell, let's turn this out to the audience. If you have questions about genetic science, about where you think genetic research should be heading, if you have thoughts on this idea of how much of you is preordained by your DNA and how much of it is environment or what you choose to do with the DNA you inherited from your parents, please join us.

ROBERTSYou can call 800-433-8850. You can email us kojo@wamu.org. You can also get in touch with us through Facebook or tweet us @kojoshow. The book again is called "The Violinist's Thumb" and the author is Sam Kean. Some of the, to me, really interesting part of this book was some of the stories of how the science became illuminated, and some of the blind alleys that people went down.

ROBERTSAnd you say at one point reading it now, you think it was all there. Why didn't you people put it together? And you know, genes and DNA weren't connected with each other. Mendelian genetics and Darwin's evolution weren't connected with each other. Do you feel like we've finally sort of all got it sorted out or are there great big questions like that still open?

KEANThere are still open questions. I think we do have a pretty good general idea of how things like Mendel's theories and Darwin's theories do mesh and work together. But yeah, there are still big questions out there.

KEANI mean, just this past week we answered, you know, we started to answer one of them about what so-called non-coding DNA does. There are questions now about how much we interbred with other species like Neanderthals or Denisovans and possibly even other species that we haven't discovered yet.

KEANSo I think there are still big questions out there in terms of our history that I think DNA can really, really help illuminate. So no, I don't think they're probably even close to being done with these kinds of things.

ROBERTSAnd where do you fall having done all this research on the idea that evolution is sort of incredibly slow and incremental or whether it proceeds by fits and starts or the punctuated model that Stephen Gould put out? You know, how does that relate? What's the analogy that you like?

KEANThat is a very hard question to answer because it seems like nature is very conservative about changing genes. Most of the mutations, the changes to DNA that you see, do lead to harmful things and it's only occasionally that you get something beneficial.

KEANBut on the other hand, some of the large-scale changes, changes to say the basic body plan, the basic blueprint of animals, you know, some of those changes might have come about through a, you know, a change and it might have happened, you know, fairly quickly these kind of things so...

KEANIt is a really hard question to answer and that is kind of one of the big questions out there. I think everyone agrees that in normal situations, evolution does happen slowly. But we don't know if every so often, you know, maybe in times of great stress or maybe just someone gets very lucky and something can change relatively quickly, probably over, you know, a few million years we're talking about.

ROBERTSRight, right.

KEANThat's quickly on some time scales.

ROBERTSThe timeframe we're talking about the idea of diagnosing people retroactively, which you spend a chapter on in the book. It seems to be a little bit of a parlor game but this idea that you can look at a portrait of Abraham Lincoln and assess his physical ailments with or without his DNA. Why is that useful other than just being sort of interesting?

KEANHum. Well, I have to admit I'm a bit of a sucker for these kind of things here.

ROBERTSI have to admit I am too so, you know...

KEANThere's no paper about some obscure emperor I won't read if it has some medical history to it. But it can, I think, shed at least a little bit of light on the people. I made a joke in the book at one point. There were like 20 different diagnoses for Charles Darwin, everything from pigeon allergies and lactose intolerance to adrenal gland tumors and narcolepsy, just so many different things. And while it may not be important to pin it down to one specific diagnosis, reading those kind of things can help illuminate what the person's life was like. What it was like to be Darwin, What it was like maybe to be Lincoln, something like that.

KEANIn Lincoln's case, Lincoln's case is a little, I think, more interesting in that there are people out there who think he might have had marfan syndrome which is a genetic disorder. And people with marfan syndrome often die fairly young and they often die fairly quickly -- very suddenly from a ruptured aorta. So if Lincoln did have marfan syndrome, you know, it's possible he might have died fairly young no matter what. Maybe he was kind of always doomed to never finish out his second term. It's not something we could ever answer, of course but at least we would know that about Lincoln.

KEANBut, as I explained in the book, the idea of trying to test him ended up being a little fraught and they ended up deciding not to do the testing for various reasons.

ROBERTSWhich -- I mean, considering there's a fair amount of Lincoln DNA around, you know. I mean, you can't go to Ford's theater without seeing the bloody whatever.

KEANYeah, there's pillowcases, there's shirt cuffs, there's all sorts of things. So I guess if there would be one historical figure we would do a genetic test on fairly easily it probably would be Lincoln because we do have samples of his DNA that we can get at without having to dig up his bones, as you would with Darwin or other people like that.

ROBERTSYeah, in Darwin's case actually dig up the floor of Westminster Abby, which...

KEANYeah, they were not too happy about suggestions about that.

ROBERTSLet's take a call from John in Falls Church. John, welcome to "The Kojo Nnamdi Show."

JOHNHello. I'm very pleased to be on your show. Your book seems to reflect something that I've been discussing with my clients for many years. And some of the obvious things are things such as why you look like your parents. It isn't described at all by, you know, the code on, you know, producing a certain protein sequence. And I've always thought that 90 percent of the stuff that genetics do for us sort of corresponds with the 90 percent of junk DNA floating around.

JOHNIt also fits -- I mean, you were mentioning viruses before, it also fits with the idea of human being a biome, not just a human being but a colony walking around 90 percent in one sense is not human, 90 percent -- if you count up the microbes in your body they constitute a number. And the number of cells in your body only add up to about a tenth of that. Conversely if you go by weight you actually weigh 90 percent human but 10 percent -- or around 15 percent nonhuman. All the bacteria in your intestines, on your skin, in your tissue, all of them very necessary for you to stay alive.

JOHNI'm pleased that you also mentioned Lincoln in that often I think about how constellations of symptoms for things like marfan can affect the way we behave. And much of the way Lincoln behaved expressing his magnificent mind could have been formed somewhat by his genetics and his situation.

ROBERTSJohn, thank you so much for your call. I have to agree with John that the total prevalence of microbes was one of my jaw-dropping takeaways from this book.

KEANYeah, it goes to show, I think, that it's not just human -- or it's not just human DNA that can illuminate our history. When you look at, you know, the history of viruses and bacteria, things like that, that can help shed light on our history too. And when you are talking about human beings, John was right, it is a biome actually. You have to work with -- your body has to work with all of these microbes to really make you who you are.

KEANAnd there's a lot of scientists who think that viruses especially were probably much more influential at various stages in our history than we might even like to think of. One of the really good examples of this is the human placenta which of course needs to -- when -- you're talking about an embryo right after fertilization -- the embryo needs to fuse with the wall of the uterus and a placenta needs to form. One of the key viruses in fusing to the uterus wall actually we probably stole from viruses and we wouldn't have the placenta that we know in mammals today had we not stolen this gene from them and kind of turned it toward our own end.

KEANSo it's one of the examples that, you know, it's a little uncomfortable to think about a virus having that much influence on us but it seems that they probably did.

ROBERTSMy guest is Sam Kean. The book is called "The Violinist's Thumb: And Other Lost Tales of Love, War and Genius, as Written by Our Genetic Code." We need to take a quick break, but when we come back, more of your calls and emails, 800-433-8850 or email kojo@wamu.org. I'm Rebecca Roberts sitting in for Kojo Nnamdi and we'll be right back.

ROBERTSWelcome back. I'm Rebecca Roberts sitting in for Kojo Nnamdi. My guest is Sam Kean, author most recently of "The Violinist's Thumb: And Other Lost Tales of Love, War and Genius, as Written by Our Genetic Code." And you can join us, 800-433-8850 or email us kojo@wamu.org. Let's take a call from Nancy in Silver Spring. Nancy, welcome to "The Kojo Nnamdi Show."

NANCYThank you very much. This is a very interesting topic to me because I have participated in the DNA carried out by an organization of Spencer Wells and the National Geographic. And I understand it somewhat but it's sort of mysterious to me that they can map your genes from when you came out of Africa all through East or West Europe and into China or else into Great Britain and do -- you know, find out through markers and so forth in those 100 and some years where you came from and where you finally settled.

NANCYAnd I don't -- you know, for instance, I am in my monochondrial mapping descended from ten generations back around from Micmac Indian, which is just fine. But, you know, I still -- I wonder what you think of that particular effort. There are many facets to it and you can get a cousin with the same markers and find out who that person is. And, anyway, I won't say anymore. I'll let you comment on it because you probably have some ideas on pro or con. So I would like to hear you speak on that. Well, thank you very much.

ROBERTSThank you, Nancy.

KEANYeah, one of the real reasons I wrote the book, what I really got excited about was when I figured out that genetics isn't just about medicine necessarily anymore. Genetics has kind of spilled over into so many other different areas of science. And one of the most exciting areas that it's spilled over into is anthropology and studying how human beings have spread across the globe. So I really think that whole idea of studying human migration and deep human history through genetics is really, really fascinating.

KEANSome of it, the basic idea is you can look at mutations in DNA, often in non-coding DNA and you can figure out how long ago different tribes might have split apart because we accumulate mutations at a constant rate. So basically -- you know, this is a little simplistic but basically the idea is you count the number of mutations that have accumulated between two different groups. And you can tell roughly how long ago the two groups split apart based on that. So that's in general the idea.

KEANBut they can now do much more sophisticated analysis for things like figuring out when human beings interbred with Neanderthals or other things like that. So I really think it's a fascinating field. I'm very excited they're starting to get into some of this work now.

ROBERTSWell, that brings up this email from Jason in Cleveland Park who says, "As you mentioned earlier, humans may have bred with Neanderthals. Have we ever bred with anything else odd in the animal kingdom or is there evidence of that and have people tried to do weird things on this front?"

KEANThere is some evidence that we interbred with another species that were a lot like Neanderthals. They were called Denisovans. They were at least around in Siberia someplace and possibly elsewhere. And there are some ethnic groups that do have this Denisovan DNA inside them. And there is one chapter in the book where I talk about some pretty hair-raising experiments that a Soviet biologist did named Ivan Ivanov in the -- I guess he was in Africa and the Soviet Union working in different places. Basically he tried to breed human beings with chimpanzees and orangutans and things like that.

KEANAnd I was shocked to hear all this and to hear that I'd never really heard many of the details of these experiments. But he went pretty far in both directions. He tried to inseminate chimpanzees and he also tried to inseminate humans with orangutan sperm. So it was a little bit of a scary story to think that he got as far as he did but, you know, it was kind of fascinating at the same time.

ROBERTSBut no humanzees running around as far as we know.

KEANNot as far as we know. Most scientists I think would say that it would probably be impossible to directly breed a human and a chimpanzee directly.

ROBERTSLet's take a call from Peter in Germantown. Peter, welcome to the Kojo Nnamdi Show.

PETERHey, thank you so much for taking my call.

ROBERTSSure.

PETEROne of the questions I've often had as we've learned more about genetic over the last decade has been tremendous the advance that has been made is, as you pointed out, we make a distinction between influences of who we are based upon our genes but also of our environment. But I've often recently come to think that that's kind of a false distinction.

PETERBecause if you really break it down, anything in our environment that we respond to is generally the result of some protein ratio or combination inside of our bodies that we sense this and respond -- excuse me -- different people respond in different ways because of the proteins that we have inside of our brain and our cells, which really come from the non-encoding DNA. So isn't it just encoding DNA versus not encoding DNA and that's really -- the environment is influencing that. But it isn't really anything different than just the impact of the proteins generated by the non-encoding DNAs?

KEANI think the way that most scientists would put it nowadays is that, as you said, it's a false dichotomy between nature or nurture. Most of them would think about it in terms of nature and nurture, really your environment and your genes working together to make you who you are. And now just your genes but your non-coding DNA too. We are finding more and more about the genetic influences on things like temperament or behavior but the more we look the closer we look, we're realizing that it is just an influence. It's not like these things are rigidly dictated about ourselves.

KEANSo while kind of the power of genes is being spread in one way, spreading into behavior and psychology, on the other hand we are figuring out that even with really basic things it is you and your environment and your temperament kind of all combining to figure out really who you are and how you work.

ROBERTSWhich is why you have identical twins who get different diseases or someone who might carry a gene that predisposes them to a disease that they never get.

KEANYeah, and everyone has known identical twins who, you know, they have slightly different personalities. And they might even look a little bit different, even though they have identical DNA. So those are two good examples of the environment kind of showing you how your genes get expressed -- influencing how your genes get expressed.

ROBERTSPeter brought up the idea that some behavior can actually be traced back to a genetic protein coding or something that you don't necessarily link to it. And the best example in your book of that is the people who hoard cats? Can you explain a little bit about why cat hoarding actually might have some genetic component?

KEANSure. This has to do with a certain microbe called toxoplasma. It’s a cat microbe and it wants to be inside cats. That's where it really prefers to be but it has learned how to colonize other mammals, usually mice but other mammals too. And what happens is when toxo gets inside mice it goes straight for their brain. And it actually can kind of manipulate their behavior in certain very strange ways. Normally mice, when they smell evidence of a cat, they're very afraid. They freeze, they -- it's a hardwired fear inside them.

KEANWhen they start -- when the toxo mice smell a cat though, they're actually attracted to it. They go toward the smell of a cat, at which point of course the cat pounces, eats the mouse and the toxo ends up back inside the cat where it wanted to be. And we know this works in mice. It's very well characterized. They know a lot about how it works. And one of the things that they know is that toxo at some point actually stole the gene from mammals to make -- or to help make, I should say, dopamine, which is a very fundamental brain chemical and influences things like motivation and behavior rewards inside the brain.

KEANThe sort of scary and more controversial part is the fact that toxo can pretty easily infect human beings as well, among many other species. And some scientists have -- you know, they've suggested -- it hasn't gone through rigorous scientific studies but they have suggested that it could explain some of the things about hoarding, specifically with cats.

KEANYou always hear about crazy cat ladies. People hoard other animals sometimes but it's often cats. And part of the reason why could be that this parasite, the toxo has gotten into their brain. It goes to the amygdala inside your brain. And it can influence possibly your behavior around cats and actually make you more attracted to cats than you normally would be. So there might be some possible biological basis for the stereotypical crazy cat lady.

ROBERTSLet's take a call from Tom in Vienna. Welcome to "The Kojo Nnamdi Show," Tom.

TOMHi, thank you very much. I really appreciate you taking my call. My question has to do with the ability of genetic material to sort of carry special skills, etcetera on through generations. And I don't mean just where you're genetically predisposed towards a particular activity or skill but I'm thinking in terms of like prodigies where you have this very, very specific skill like piano or chess or something like that where something is born with the ability to deal with just, you know, that particular context and they're so good at doing it.

TOMAnd, I mean, is there any study -- and maybe it's in your book, I don't know but as far as where somebody learned something during their lifetime or becomes good or skilled at something that somehow that proclivity can be passed on through the genetic materials. Can you comment on that?

KEANSure. This is an area that is difficult and scientists are still working on it trying to sort through. Whenever you're dealing with human behavior it really does get complicated because there's genes involved, there's culture involved. There's so many different factors. There probably are genetic influences that do help you do things like be very good at music or something like that.

KEANOne thing I have heard that some scientists thing is that when you're talking especially about prodigies, people who seem to come from nowhere, it might not be, you know, having one or two genes. It might be a combination of lots of different genes. And you kind of get all of those genes together, kind of a perfect storm of all of these genes and genetic influences coming together in one person.

KEANAnd part of the reason that it might be hard to say pass that trait onto your children, is that your children, of course, are not going to get all of the genes you had. You're going to have to combine them with another man or woman, and in that case, that sort of felicitous combination of genes might get lost. It might get reshuffled, or you might lose some of the key genes in there. So I think there are definitely genetic genes that you can pass on that can kind of give you a boost, kind of a natural talent boost in some areas.

KEANBut when you're talking about people who are really prodigies in this area, it might be a little more complicated than just one or two genes. It might be a lot of genes working together.

ROBERTSI think Tom also brought up this idea of whether or not you can pass on acquired skills...

KEANMm-hmm.

ROBERTS...which was sort of an early idea in genetics, and then dismissed completely. You know, you couldn't die your hair red and expect to have red-headed children, but now that's a slightly blurrier line with the field of epigenetics.

KEANYeah. This is something that goes all the way to an old Frenchman named Lamarck, and for a long time, he was sort of like the evil villain of the science books. They would put him up there and they would say look at this terrible idea this man had, and now we know so much better nowadays. But as you said, things have kind of come back around, and we obviously aren't going all the way back to Lamarck's theories. He would say that, you know, if a blacksmith was swinging his hammer all day he would get big muscles and then his children would automatically have big muscles.

KEANIt's not so simple like that, but we do know there are some cases in -- through something called epigenetics where you can sometimes pass down certain experiences to your children. Oftentimes this happens when you see famines during wars or, you know, in Africa their starvation or in Mao China, things like that, where you see widespread hunger, and it can cause changes, not to the DNA of the children, but to how the DNA works, how it gets regulated, how the genes get turned on and off, and the children, their health can be different than people who were gestated during times when there weren't famine.

KEANSo we are starting to see that acquired characteristics or experiences in some limited cases can be passed down to different generations. So it's an exciting field.

ROBERTSMy guest is Sam Kean. The book is called "The Violinist's Thumb." We need to take a quick break, but when we come back, more of your calls and emails. The phone number 800-433-8850. Email kojo@wamu.org. I'm Rebecca Roberts sitting in for Kojo Nnamdi, and we'll be right back.

ROBERTSWelcome back. I'm Rebecca Roberts sitting in for Kojo Nnamdi. My guest is Sam Kean. His book is called "The Violinist's Thumb," and we are taking your questions about genetics, about the interaction of genes and environment, how we know what we know about our DNA, what we still don't know. You can join us at 800-433-8850, or send us email, kojo@wamu.org.

ROBERTSWe have an email, Sam Kean, from Helen in Gaithersburg who says, "It seems that so many scientific discoveries made today, like the God particle, require equipment like particle accelerators that cost billions and billions and billions of dollars. How did scientists in the early 20th century, or even before that learn about genetics or DNA with the equipment available to them? It's hard to believe they could learn so much with just microscopes."

KEANThat is a good question. One of the things that they really did was they started focusing on simpler creatures like animals and a lot of the very earliest big discoveries in genetics were made through fruit flies especially. They were kind of the work horse of early genetics, but there were a lot of other creatures they looked at too, things like grasshoppers. Mendel worked with pea plants. So a lot of these just involved studies of other creatures and kind of watching them and focusing on traits with them.

KEANFruit flies turned out to be probably the best creature for this for various reasons. They breed very quickly so you can get a new generation every two weeks or so. They live on basically rotten fruit, so you can go to the store, buy some bananas as they were doing in the early days and just let them rot, and fruit flies are perfectly happy, and you can put a thousand in a milk bottle on a shelf and they will just sit there forever and ever perfectly happy.

KEANSo what they did, to basically answer your question, was the just bred as many animals as they could, and looked for patterns in them, and that's how they really discovered the fundamental things about how genes basically work. And then in the 1950s and things, after they discovered the structure of DNA, they had to start working with things like RNA, and then it was a lot of biochemical work. That's really where everything shifted too, and we're kind of still a little bit in that phase today. We're kind of moving more toward doing a lot of computer work, simulations, a lot of kind of information theory, but we're still a lot kind of the biochemical phase as well.

ROBERTSWell, it is amazing, looking at the conditions under which some of these remarkable things were discovered. I mean, you talked about the fruit fly up at Columbia, which was crowded and covered in rotting fruit, and, you know, Sister Miriam who did these experiments with this massive nun's headdress that limited her peripheral vision and, you know, people working in basements and kitchen hallways and in freezing cold temperatures, and it's sort of extraordinary they did what they did.

KEANYeah. They were definitely heartier back then so I have to swear -- yeah. People working in castle kitchens, the man who discovered DNA, Frederick Miescher, discovered it in the laundry room of an old kitchen. And the kind of famously dirty fruit fly room at Columbia University was about 16 feet by 23 feet I think were the dimensions. They had eight desks in there. They had hundreds of bottles of milk that they had basically stolen from stoops and the cafeteria, fruit flies in every one of them.

KEANThere were mice running through, there were cockroaches. It was just a filthy, smelly, awful place, but from it, came most of the great discoveries of modern genetics.

ROBERTSLet's take a call from Nick in Fairfax. Welcome to "The Kojo Nnamdi Show," Nick.

NICKHey, thanks for taking my call.

ROBERTSSure.

NICKWe've talked a lot about, you know, where the genetics have gone, how it's affected people. I'm curious as to where it's going, and I think more importantly, can we head off the (unintelligible) zombie apocalypse?

KEANNo. No chance.

NICKThank you.

KEANYeah. That is something a lot of people are debating, and especially people want to know about well, can we sort of actively manipulate our DNA kind of, you know, the stereotypically in a test tube, and change our characteristics or make designer babies, things like that. There scientists working right now who are looking at using virus DNA specifically, to basically cure genetic diseases. Viruses have the talent to basically inject DNA into our cells and kind of interweave their DNA with our DNA which oftentimes is to our detriment, but if you can kind of fix things so that they're giving us good, beneficial DNA, that can be to our benefit, and can hopefully cure diseases.

KEANThe other -- one of the other areas I really think is exciting is using DNA outside of the body in things like computing. There was a paper a couple of weeks ago that talked about using DNA basically to store information, like you would traditionally think about on a computer. And DNA can store information at a much, much higher density than a lot of the chips, the silicon that we have. They put an entire book, a bunch of pictures, and I believe some sort of rudimentary computer program on just a very, very tiny amount of DNA, and they were able to store it, recall it, do everything they wanted to do.

KEANSo there's a lot of people excited about the idea of using silicone and DNA together as kind of the next generation of computers. So there are different ways it could go both within biology and outside of biology as well.

ROBERTSThat's extraordinary, especially considering that one of the reasons it took scientists a little while to recognize how important DNA was was because it seemed so simple.

KEANYeah. That's the basic idea is, you know, scientists didn't understand that DNA was important in heredity because there's just four letters it, it seemed like kind of this rudimentary stunted alphabet, but the simplicity turns out to be a big, big benefit for -- in various reasons, and you can actually control DNA and control kind of how it fits together and how it works on a molecular scale, much more easily than you can control a lot of other substances. So it turns out to be a really great tool for things like nanotechnology, or trying to build better microcircuits.

ROBERTSWell, one of the things that I definitely took note of reading the coverage of the -- some of the discoveries about non-coating DNA this week is that these switches didn't necessarily appear to be close to the genes they were affecting when the DNA was unrolled to study.

KEANMm-hmm.

ROBERTSBut because DNA has to cram itself, this long string, into this teeny tiny little web of hairball of, you know, of a mess...

KEANMm-hmm.

ROBERTS...that actually when it coiled up on itself, the switches were near the genes.

KEANYeah. That's another kind of exciting area is looking at the three-dimensional structure of DNA. We're kind of used to thinking about DNA the way you read a story in a book. You just go line by line. But, you know, you said at the top of the hour that there's six feet of DNA inside every one of our cells, and it has to fit into a nucleus that's often, you know, only about a thousandth of an inch wide. So you have to scrunch it down incredibly far, which means taking parts of chromosomes, bits of DNA that wouldn't normally be near each other, and putting them in close proximity.

KEANSo perhaps we need to look at the 3D structure of our chromosomes to really figure out what they're doing. And I think scientists do have at least a start on this. We know that certain chromosomes tend to work together very often for whatever reason, probably because they have genes that do need to be very near each other. So that's another area they really started to get into was the long -- the bigger term structure of DNA.

ROBERTSWell, the idea of chromosomes twisting around each other or interacting with each other brings up what I thought one of the more terrifying stories in the book, which is the Philadelphia swap.

KEANYeah. That has do with chromosomes 9 and 21 inside you, and when you're talking about chromosomes, you have two copies of every one, and it happens pretty often where say your two copies of chromosome 9 might exchange information. They can trade tips or trade whole arms. It's called crossing over. Every once in a while though, two chromosomes that shouldn't be trading bits do trade bits, and in this case with the Philadelphia swamp, or the Philadelphia translocation scientists would probably call it, with the Philadelphia swap, you get an exchange between chromosomes 9 and 21.

KEANAnd what that does unfortunately is it leads to a very specific type of cancer. It's a leukemia, a very aggressive leukemia that can often kill people very quickly, and the story that I used to illustrate this in the book is -- it is a little scary to think about, a woman actually got -- she was pregnant, and because of some various genetic changes, including the Philadelphia swap, the cancer that she had actually infiltrated her fetus, and...

ROBERTSOr maybe her fetus gave her the cancer.

KEANYeah. They weren't sure at first actually what had happened, whether it had gone from mother to fetus or fetus to mother, but they knew that somehow the cancer had gotten transmitted from one to the other, which normally shouldn't happen. You know, cancer in pregnant women isn't that uncommon. It happens once maybe every thousand or so pregnancies, but the placenta should block the cancer either from getting to the fetus or getting out from the fetus, but in this case, something broke down and it took a look of genetic detective work to figure out exactly what had happened, and it was really a fascinating story of how they unraveled this and how they figured out the genetic basis of this very aggressive, very scary cancer.

ROBERTSI think we have time for one more call. This is John in Silver Spring. Welcome to "The Kojo Nnamdi Show," John.

JOHNHi there. Yeah. I just -- you've moved on a little bit from the original issue I wanted to talk about which was epigenetics, but since we're talking about passing on genes to children, this could be relevant too in that during the 1930s, the American Eugenics Movement, they were talking about criminality and other social ills are passed from parent to child which gave rise to sterilization of criminals, the poor people, the insane, things like that, which are still on the books in some states.

JOHNDoes epigenetics suggest that criminality can be passed on from parent to child, or abuse, and how does that influence the idea that we have about things like gene therapy and particularly germline gene therapy?

KEANI think the other scientists would say that it would be far too simplistic to say something like criminality could be passed on. I think criminality is kind of a too broad, too diffuse an idea for that to be passed on directly. Something like abuse, there is evidence that at least there are lingering effects of abuse, and again, it would be too simplistic to say that if you get abused, you know, you're automatically going to abuse the next generation and it will just keep getting passed down over and over.

KEANBut we do know that there are lingering effects of those kind of things, and some of them at least do get passed on through epigenetics. So there is some evidence that at least aspects of these kind of thing can get passed down. In some cases though, you know, you might not even have to go into the genetics for these kind of things. It might just be a purely environmental fact, or more likely, it is genes and environment working with each other once again to kind of pass these different traits down.

ROBERTSBefore I let you go, you need to tell everyone why they shouldn't eat polar bear liver.

KEANOkay. That was another one of the stories that I really did not know much about before I started the book.

ROBERTSWell, why would you?

KEANYeah. I guess why would I. The story is basically about a bunch of polar explorers in the Arctic. They went up there without really knowing what they were doing. They were going around shooting polar bears, killing them. Sometimes they would get stranded up there. Polar bears were the only food they would be able to find, and they found out the hard way over and over that polar bear liver is actually saturated with vitamin A.

KEANThere's just a ton of vitamin A in there. Vitamin A's a very important genetic switch. Very important nutrient for a lot of different processes in the body. It helps turn DNA on, things like that. And when you eat too much vitamin A, it can different effects in the body, especially in skin cells, and one of the really horrific side effects is that it makes your skin basically start peeling off in sheets, and there are many, many eyewitness descriptions of people's, you know, ears coming off in a whole cast, the soles of their feet completely peeling off, and all these different stories. So do not eat polar bear liver if you're ever stuck in the Arctic.

ROBERTSWords to live by. Sam Kean, the author of "The Violinist's Thumb: And Other Lost Tales of Love, War, and Genius as Written by Our Genetic Code." Thank you so much for being here.

KEANThanks for having me.

ROBERTSI'm Rebecca Roberts sitting in for Kojo Nnamdi. Thank you so much for joining us. Kojo will be back tomorrow.