#106 — Humanity 2.0
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Summary
Jennifer Doudna is a biochemist, an investigator, and a researcher at the Howard Hughes Medical Institute and the Lawrence Berkeley National Laboratory. She is the author, along with Samuel Sternberg, of the book, A Crack in Creation: Gene Editing and the Unthinkable Power to Control Evolution. And she is credited as one of the inventors of the CRISPR-Cas9 gene editing technology, which is the topic of today s conversation. We get into all the details and the ethics of this technology, and Jennifer s time was short, so I could only schedule about an hour with her. But I was great to have her walk me through the details, and I trust you will leave this podcast as I did, knowing much more about where this technology is at present and where it is likely to go in the future. Sam Harris Making Sense is a podcast produced by Sam Harris and the team at The Making Sense Project. They don t run ads on the podcast, and therefore, therefore, are made possible entirely through the support of our listeners. Please consider becoming a supporter of what we're doing here, by becoming a member of the Making Sense Podcast. You'll get access to all sorts of amazing resources, including blogs, podcasts, books, and more. Thank you for listening to Making Sense: Podcasts, and much more! - Sam Harris, PhD, PhD - Making Sense, and (p. ) (ABOUT THIS PODCAST SERVER. (PRODUCING THIS EPISODE) - THE MADE MADE SENSE PRODUCER AND THE MATERIALS AND OTHER THAN THAT AND OTHER LINKS). (THAT'S AVAILABLE INCLUDE) (PRODYNAMES AND MORE) ) (CRISPR & OTHER THIRD THAN A THIRD-PRODY AND SOCIAL MEDIA) (VOCAL SUPPORTED INTROLEPRODCAST, BECAUSE I'S NOT JUST A VOCABULARY AND A VOTING IN A PEDCAST AND A PAPER AND A VIDEO AND A PLATO AND A FEDERATION AND ANOTHER THIRD PLACE AND A SOCIOLOGY AND A DEDICATE AND A CREATING A VOTE IN A VEOTHEPRONE AND A BIRD AND A PROTEIN AND A TUNNTRY AND A THOTCAST)
Transcript
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She's a professor in chemistry in the molecular and cell biology departments at the University
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She's also an investigator with the Howard Hughes Medical Institute and a researcher
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in the molecular biophysics and integrated bioimaging division at the Lawrence Berkeley
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She is one of the world's experts on RNA protein biochemistry and, in particular, CRISPR biology.
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And she's the author, along with Samuel Sternberg, of the book A Crack in Creation, Gene Editing
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and the Unthinkable Power to Control Evolution.
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And Jennifer is credited as one of the inventors of the CRISPR-Cas9 gene editing technology, which
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Jennifer is a rock star scientist, and I could only schedule about an hour with her.
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It was great to have her walk me through the details of CRISPR.
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And I trust you will leave this podcast as I did, knowing much more about where this technology
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is at present and where it's all likely to head.
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So, without further delay, I bring you Jennifer Doudna.
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So, you are a co-inventor of CRISPR-Cas9, which is a gene editing technology that we'll talk about.
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Before we get into this, perhaps you can just give a kind of potted summary of your background
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Well, I'm a biochemist, so I'm somebody who studies molecules and how they work.
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And I've always been interested in evolution and the way that cells have evolved to use
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And that's actually how we got into the whole area of gene editing.
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Now, I know there's some controversy about who should get credit for inventing CRISPR-Cas9.
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I think there clearly is no controversy that you are one of the world's experts on this.
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Is there anything you want to say about the controversy?
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Or is it kind of a distraction as far as this conversation is concerned?
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Well, I guess all I would say is that my work with Emmanuel Charpentier was, you know,
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going on to really, I would call it a curiosity-driven project that was aimed at discovering how
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So neither of us were aiming to create a technology.
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But the work that we did uncovered the activity of a protein that can be programmed to find
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And with that understanding, it was pretty obvious that this was going to be a great technology.
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Okay, well, let's talk about CRISPR and that protein.
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But before we do, it might be good to give a very quick remedial summary of some basic
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I think we have a fairly educated audience here.
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But everyone, I think, can do with a primer on DNA to RNA to protein.
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And, you know, because we're going to be talking about just the mechanics of gene editing here.
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So can you give us a few minutes of basic biology here?
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So I guess we could start by pointing out that people probably are familiar with the idea that
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So it's really the chemical that stores information in cells and allows cells to grow and develop
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And the way that cells use that information is mostly in the form of proteins.
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So the information in the DNA is converted into proteins by a process that creates the protein
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And the intermediary in that process is kind of what I like to call a throwaway copy of
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the genetic information, which are molecules of RNA.
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And what has emerged over the last probably two decades is that RNA molecules are not just
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throwaway copies of the genome, but they are actually molecules that have a lot of interesting
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And that's actually what I've always been interested in in my own laboratory, is the
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role of RNA molecules that are involved in controlling the flow of genetic information
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and helping cells decide when and how to use the information that's stored in the genome
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And the story of CRISPR, the story of this gene editing technology, is kind of interesting because
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it really involves all three of those types of fundamental molecules, DNA, RNA, and protein,
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because it's a protein that is involved in the, is really responsible for cutting DNA
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The places in the DNA that get cut are defined by molecules of RNA that the protein, which is
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called Cas9, holds onto, and the places in the DNA that get cut are the sites in the genome
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where editing occurs, where permanent changes are made to the genetic code.
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CRISPR has been described as part of the bacterial immune system.
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And what does the CRISPR sequence do in that context?
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So viruses infect bacteria actually all the time in nature.
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And so bacteria have a very effective way of defending against viruses by storing pieces
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And then they use that, they use that stored viral DNA sequence.
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There are actually multiple, multiple sequences coming, you know, one representing each virus
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So you can think of it sort of like a genetic vaccination card.
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And then those, those stored viral DNA sequences are copied into RNA.
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And then those RNA molecules assemble with the Cas9 protein to direct it to sequences that match
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In other words, sequences that are, uh, belong to viruses.
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And when that match occurs, then the, the Cas9 protein works like a, like a molecular scalpel
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and cuts the, the, the viral DNA and, and, and basically allows the cell to, to, to destroy it.
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So again, this is semi-dense material and you don't have the benefit of visual aids here.
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So I just want to make another pass on this just to make sure everyone has a picture of
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It's a combination of protein molecule and RNA, which is really informing its behavior, right?
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So you have an RNA sequence that matches a sequence in the DNA, which determines what part
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And this is something you've discovered in bacteria, but which can be used as a kind of
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molecular scalpel in eukaryotes like mammals, such as ourselves.
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And this then becomes a way of targeting with a precision that we didn't have before spots
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So I guess I'm interested a little more in the mechanics of this.
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So what are the chances that the CRISPR-Cas9 technology will cut in the wrong place in the
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I mean, does there have to be a complete complementarity between the RNA and the DNA, or is there
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I think the amazing thing about the CRISPR-Cas9 technology is that it's really pretty accurate,
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So I think what's emerged over the last few years that people have been using this, and
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it's probably worth mentioning that this technology took off incredibly quickly.
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It was adopted very, very rapidly after our 2012 publication, and there are now probably
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thousands of people around the world using this as a tool in all sorts of systems.
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And the good thing about that, or one of them, is that it's meant that there's been very
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rapid development of the technology as well as understanding of how it works.
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And one of the things that's emerged is that this tool is, you know, it's accurate enough
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to make precise changes in even very large genomes, like the human genome or plant genomes.
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And when people have sort of as, I think as people have become more sophisticated about
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using it, ensuring that the Cas9 protein is used in limiting amounts in cells, not present
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in huge quantities and not hanging around for too long, that it's actually remarkably accurate
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It's possible to find off-targets, but you have to look pretty hard.
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And can you edit a single base pair, or do you have to deal with longer sequences than that?
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Is it always a matter of inserting more DNA, a variant sequence, or can you simply cut and
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Yes, you can cut and remove, or you can cut and replace.
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The removal part turns out to be easier technically to do than the replacing part, but both are
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So, again, this is so counterintuitive in ways when you actually picture what's happening
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here, because anyone who's taken biology in recent memory will know that the genetic
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material inside our cells is in the nucleus, and it's bound very tight.
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The chromosomes aren't laid out in the pretty way that they are when we picture them in
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And now you've sent CRISPR, this little machine, into the cell.
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We'll talk about how you can target tissues later on.
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But this goes into the cell and moves all over the genome and is searching for the sequence
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to which it is the mate, and so that it can find the place to cut.
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How do you get full coverage of a genome, and how quickly does this happen?
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If we could take a video camera inside a cell, what would we be seeing there?
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Not quite a video camera, but it's been possible to make fluorescently labeled versions of the
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Cas9 protein that can be visualized in live cells.
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So, you can basically watch these little dots of light moving around in the nucleus.
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And when you do that kind of experiment, what emerges is that this is a protein that has
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very fast kinetics, so it's moving around the nucleus incredibly quickly, much more quickly
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than what you see for other kinds of proteins that are, you know, existing in the nucleus.
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And what's thought to happen is that this protein is rapidly sampling different sections along
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the sequence of DNA, and it is quite remarkable to think about it because, you know, we're
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talking about billions of base pairs of DNA in the cell, but somehow this protein very
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quickly samples along the DNA sequence looking for a match to the guide RNA sequence.
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And one thing that's important to keep in mind is that it's not a single protein that would
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be in the nucleus, but instead many, many copies of this.
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There might be, you know, thousands or tens of thousands of copies that are all searching.
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And when one finds its target site, then it makes a cut and the edit occurs.
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Now, are the sequences of DNA unique enough so that we're not getting redundant cuts?
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I mean, if you send a, you know, a 10-nucleotide sequence as your kind of search code, are we
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expecting that to be the only place in the genome that would get modified, or just by dint
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of numbers, you're going to be altering something you didn't expect to alter if you do that?
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Well, in one of those interesting serendipities of science, this Cas9 protein actually uses a
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So it's 20 letters that it's looking for, 20 letters in a row.
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And if you do the math, that's just about what you need to uniquely define a sequence
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So now we have a human being who has a variety of genes that are not as perfect as they might
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be, and we'll talk about the conditions for which we have some understanding of the underlying
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genetics and, you know, what could be modified here.
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But let's say we know what genes we want to alter.
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How would we target CRISPR to specific sites in the body?
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And presumably, these insertions would sometimes need to be tissue-specific.
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You wouldn't want to send this everywhere, right?
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And I think you're putting your finger on what I think is one of the critical challenges
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for gene editing in the clinic going forward, which is just what you said.
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How do we deliver these editing molecules into the right cells at the right time?
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One of the ways that this can be done today is actually by delivering into cells that are
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So, for example, people are working hard on correcting mutations that cause blood disorders
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because the blood cells can actually be taken out, edited, and replaced.
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So I think that's one strategy that gets around the issue of trying to deliver something like
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If you wanted to get it into every cell in the body, what would be the methodology?
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Well, that would be hard, even using a virus, because viruses tend to target particular kinds
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So you might have to use a cocktail of viruses that are able to get into many different types
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But I think what is typically envisioned is that you might be able to use viruses that
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would deliver into specific parts of the body, for example, into the liver or into the brain,
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and create edits that would alleviate disease in cases where the gene edit is necessary just
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And what is the time frame over which this would occur?
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I mean, just so again, we'll talk about how difficult this might be in practice.
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But let's say we know the gene we want to edit, and we have the way to target the relevant
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tissue, and someone has a disease born of this malfunctioning gene.
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How quickly would CRISPR change their genome and cancel the disease?
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I've seen some data in animal models of disease, for example, in mice, where mice get an injection,
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and within a matter of, you know, a couple of days, you can start to detect edits in the
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DNA of the cells that have been targeted in the treatment.
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So I think the idea in principle, and I think this is something the field is working towards
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doing, is that gene editing would be a fairly fast kind of treatment.
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And furthermore, and this is actually very important to appreciate, is that it's a different
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kind of therapy because it's really a one-and-done treatment in principle, right?
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The idea is you would do this once, and then you don't have to do it again.
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I really want to get into the ethics of all of this, because that is quite interesting,
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But before we do, so what are the most plausible first uses of this?
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