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Chapter 1: What is the main topic discussed in this episode?
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You're listening to Shortwave from NPR. Short Rivers, I'm going to take us back to high school biology, the genetics chapter. You may have learned that the human body is made up of trillions of cells, and inside those cells are DNA molecules, those strands that contain the genetic code that makes you, you. But here's something that may surprise you and you may not have learned in school.
that DNA is not the same for every cell. And that's because DNA is constantly changing. There's actually trillions of mutations happening in your cells every day. This is Roxanne Comsey. She's a science journalist and a contributing writer at The Atlantic.
We're just constantly in flux, partly because there's just wear and tear, like genes will get turned on and sometimes things will break and then enzymes will come in and try to fix it, but they won't always do the best job fixing it. So we are kind of a landscape of genetic diversity, each of us, just by nature of all the DNA changes, all those errors that pile up over the course of our lives.
By the way, scientists have known for decades that our genes mutate. It's just that in the last decade, DNA sequencing has gotten so much more powerful and precise that scientists can now read the genetic code of individual cells.
There's been this possibility to kind of do a census of the cells in a body and figure out which ones have which mutations that the other cells don't have. So then here we are grasping this diversity, this genetic diversity that exists inside us.
And it turns out there is a lot of genetic diversity going on inside us. So much so that Roxanne wrote an entire book about it called Genetics. Beyond inheritance, our ever-mutating cells and a new understanding of health.
People hear the word mutation and they immediately think about something negative. But there's also good things that can happen with mutation.
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Chapter 2: What surprising facts about DNA mutations are discussed?
And if our DNA is always changing, then who are we really? I'm Emily Kwong. You're listening to Shortwave, the science podcast from NPR. Roxanne, so usually when we talk about genetic mutations, it's because something extraordinary arises from it, like the formation of an entire species eventually or an inherited disorder. But in your book, you say mutations are ordinary.
They're as common as salt. They are happening all the time. What kinds of mutations are happening all the time?
So yeah, I guess I could have called this book like Everyday Mutations. I mean, you and I are mutating as we're having this conversation. People listening to this are mutating as they're listening. It's something kind of ongoing. It's kind of the background noise, if you will, of our lives. Because the cells are copying and just making errors all the time.
Yeah, there's cell turnover all the time. Like our skin cells, you wouldn't believe how many skin cells we shed. Our blood is turning over constantly. And it has implications for our health, even these smaller scale mutations, because there's a lot of mutation happening and a lot of it doesn't matter in our cells.
But every once in a while, there is something that happens and it's not going to cause a new species. It might be an evolutionary dead end because we're not going to pass it on to the next generation. But for the vast majority of the mutations in our bodies, what matters is where it falls in the genome.
And if it falls in a place that matters and that that cell reproduces or replicates itself, that's when you get into a situation where a spontaneous event can have really profound impacts on our health.
Are there any specific environmental factors or behavioral factors that trigger certain kinds of mutations?
So we know that things like sunlight obviously cause our skin cells to mutate. That's what's linked to skin cancer, for example. If you have good quality sleep, if you sleep well, that is actually linked to fewer mutant cells.
But what I found really striking is that we now have the ability to dissect our mutations so much that scientists can actually look at the signature of your mutation, so where they fall in the genome. And actually tell you if you have been smoking tobacco or chewing tobacco. Like that's how refined a picture we're getting of how our behaviors affect ourselves.
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Chapter 3: How has DNA sequencing changed our understanding of mutations?
And what they found out is that in addition to having the inherited disorder, so the mutation that would have caused their immune systems to malfunction, they actually had second corrective mutations that were actually normal. allowing their immune systems to function well. And this isn't just a fluke.
So that was with one immunodeficiency, but they found it in patients like, I don't know if people are familiar with Duchenne muscular dystrophy. Now, this is a disorder that's kind of a progressive muscle disease. It's tragic. It's extremely tragic because people die so young. There was a case that, again, in like the 90s where
There was a patient who just wasn't progressing as they thought that he would. And it was very interesting because it was one side of his body was doing better than the other.
And then they did the kind of cellular analysis and they found that actually earlier in his development, one of his cells had actually acquired spontaneously a corrective mutation that essentially fixed the muscular issues that would have happened. And it's kind of interesting as case examples, but what you have to understand is that this then points to new treatments.
Some people have called it natural gene therapy. Oh, yeah, yeah, yeah. Your book talks about natural gene therapy in the context of skin disorders, muscular disorders, and anemia, these kinds of spontaneous corrective mutations.
It's amazing, right? Uh-huh. I mean, I look at our bodies as just… Completely dynamic. Like we are not static in any way. It's almost like we're constantly playing the lottery in ourselves. And sometimes we get lucky. And I think what we can now do because we have the DNA sequencing technology is we can...
learn from that luck and we can replicate it and in fact you and i our immune systems benefit from the process of mutation that's one area in the body where mutations are critical to our health instead of detrimental yeah that's a good point i mean vaccines are really capitalizing off our ability to mutate right they wouldn't work if our cells couldn't do that yeah so um
You write in a different chapter called The Next Generation, quote, Most of the time when doctors talk about the risk of genetic problems in parents' reproductive cells, they focus on egg cells. An embryo, of course, comes from an egg cell and a sperm cell when they come together. But scientists have started to look also at sperm cells and how their genetic mutations could shape the embryo.
What has research found there?
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