6 ms·

CRISPR Gene Editing

108 points by PieSquared 11y ago

ProAm 11y ago
Great podcast on CRISPR from radiolab [1] [1] http://www.radiolab.org/story/antibodies-part-1-crispr/ http://www.radiolab.org/story/antibodies-part-1-crispr/
- cheapsteak 11y ago
  One of the main arguments given against splicing human embryos on there was that embryos couldn't decide for itself whether it wanted it. I think that's kind of absurd. The decision that impacts it the most has already been made for it - existence. If we take the Buddha's view that life is suffering, then it has been decided that is suffers. Compared to that, what sin is it to give it whatever advantages a few spliced genes can offer?
avinashv 11y ago
While the author is pretty clear that "only a passing knowledge of modern microbiology" is necessary, I think that understates some of the technical language in here. I really laughed at the line, "Silencing a gene with CRISPR/Cas is incredibly simple." Still, I learned a lot. This is the closest I've come to feeling like I know what's going on in CRISPR. CRISPR has got to be one of the most important scientific achievements of the past few decades, right?
- DaveWalk 11y ago
  Absolutely. The movement from discovery (from the unsexiest of all fields, bacteriology!) to a reliable tool is unprecedented[1] in the scientific realm. For my money it is easily on track for a Nobel Prize: it allows mankind to examine with precision unknown just years before. [1] I see a parallel to short hairpin RNA gene silencing (shRNA, a.k.a. RNA interference, RNAi). A breakthrough discovery, at use at the bench in less then a decade, and an easy clinch for the Nobel Prize. CRISPR has gone even faster.
  - dnautics 11y ago
    > The movement from discovery (from the unsexiest of all fields, bacteriology!) to a reliable tool is unprecedented. Uhm, restriction enzymes? for the uninitiated: https://en.wikipedia.org/wiki/Restriction_enzyme https://en.wikipedia.org/wiki/Restriction_enzyme (basically, restriction enzymes are what CRISPR is basically set to replace for complex systems/organisms where restriction enzymes are too weak; although for simple systems restriction enzymes are waaay simpler)
    - dluan 11y ago
      I really wonder if it's just a matter of time before you get clans of technology in bio. Akin to the PHP vs Ruby vs Node vs Go evolution. At the end of the day, they are just tools, and tools however technically shiny, don't by themselves deliver better end products.
      - dnautics 11y ago
        That's already happened with NG DNA assembly. PIPES cloning vs. Gibson Assembly vs. ColdFusion, etc. In the case of restriction enzymes, though, they've been around in continuous use since something like the 70s, they're very well characterized, NEB has had a continuous research program where they've been optimized out the wazoo. Technically speaking they are fundamentally simpler than CRISPR (one component, vs. 2). They also are more generally useful when your genetic manipulation is done outside the cell. So there's a clear tooling difference in CRISPR/RE. Most people who use CRISPR, will use REs in the process of make the DNA piece they're putting in alongside the CRISPR. You'd be a fool to use CRISPR in E. Coli or Yeast. So 'clan'ing ain't gonna really happen here.
- neuronic 11y ago
  Yes. The next time some "What is the most promising technology?" thread pops up on reddit, you can safely post CRISPR. Depending on how things go with the patent stuff and the technology itself, sooner or later this will absolutely transform our lives. We are looking at the incubation of a technology that may easily save millions of lives (over a long time frame). Potential for misuse is near infinite though - imagine a privatized CRISPR inaccessible to the sub-$50 million/ year crowd. The limitations of CRISPR really do appear to be few though. Lots of techniques and methods will be developed and figured out in the next years. It allows us near complete control over the most essential biology. And all that in vivo. The road ahead is rough but I am confident that CRISPR can become the magic tool I just described. It will be black and white magic. Question is which will dominate?
  - zardo 11y ago
    Potential for misuse is near infinite though - imagine a privatized CRISPR inaccessible to the sub-$50 million/ year crowd. I can imagine a lot worse than that. Imagine genetic engineering gets dirt cheap, and that does seem to be the direction we're headed. Novel pathogens are going to be a lot easier to design than treatments and preventative measures to protect against them. How do you stop the proliferation of bio-weapons? I'm thinking that would be about as easy as stopping the proliferation of malware.
    - technotony 11y ago
      One major difference is that you have to order your DNA typically from a third party provider and they can screen for pathogenic sequences. We could probably stop malware if we could screen all the code before anyone was allowed to run it. I think the current system is reasonably robust for stopping novel syn bio pathogens. In my mind the big risk comes with home based DNA printers. There are several close to getting to market (eg http://www.kilobaser.com/ http://www.kilobaser.com/), at that point we lose control over what gets printed and then maybe there are concerns... though I do think creating a pathogen is really hard and most likely to end up killing the creator before anyone else.
      - 11y ago
dperfect 11y ago
Can someone help me understand the main differences between CRISPR and traditional genetic engineering that has been done for many years now? My understanding is that we've had technologies to selectively modify DNA for some time, but perhaps it hasn't been as targeted or reliable as CRISPR? One thing that stands out to me (especially from the radiolab episode) is that it sounds like CRISPR isn't just gene editing in the sense of engineering something in a lab; it's gene editing in an already living organism. If DNA is anything like an organism's "source code", once the code is "shipped" (organism is conceived), traditionally we tend to think of that code as being locked/frozen. It sounds like CRISPR is akin to modifying the code live - "in production", so to speak. Is that a fair analogy? Edit: to explain, when I say "in an already living organism", I'm referring mostly to a developed, multi-celled organism. I understand that traditional techniques also use living cells, but the radiolab episode makes it sound as if a full-grown adult human may someday get a live "DNA upgrade" - at least to applicable portions of the body - via CRISPR, e.g. to remove a genetic predisposition for developing a particular disease. To me, that would be substantially different (in practical application) from genetically engineering something like a gamete or a single-celled bacteria.
- cgearhart 11y ago
  CRISPR performs pattern matching on the DNA sequence immediately preceding the cut location where new sequences are added. While we have had CTRL-X and CTRL-V for awhile (in the other gene modification techniques you alluded to) CRISPR provides a cursor that allows us to precisely control where the CTRL-V takes place. As for updating "live" code...that's a flawed, but not completely wrong analogy. Other techniques do rely on modifying the genome before "production", and in that sense CRISPR does enable us to edit DNA in cases that would have been impractical before, but it still basically requires performing the modification on each cell individually -- so there are still practical limits on deploying the technique.
  - eggie 11y ago
    Precise targeting of genomic cuts has been possible for some time, but more expensive: https://en.wikipedia.org/wiki/Zinc_finger_nuclease https://en.wikipedia.org/wiki/Zinc_finger_nuclease https://en.wikipedia.org/wiki/Transcription_activator-like_effector_nuclease https://en.wikipedia.org/wiki/Transcription_activator-like_e...
deleted 11y ago
[deleted]
brock_r 11y ago
Will anyone here be really surprised if it turns out ribosomes are duplicating machines designed by some alien race? The entire process of reading the DNA code and turning it into proteins is just amazing.
- Balgair 11y ago
  I understand the downvotes, but the wonder here with biology that the OP has is well placed. I came into bio from DoD/Physics and am constantly astounded by what nature has made. I mean, it's been ~4 billion years and the generation to generation time is ~20 minutes (~1.1E14 generations total), so I think we all can expect a fair bit from nature, but still, she is really clever. I do think about this as well. The complexity, the reliability, the ability for nature to do what she does even in the face of all the thermal noise and viruses and enviroment, it really seems like there must be someone making it happen. Alas, no though! As far as we can tell, it's all just evolution and chance on a planet wide stage with microscopic actors. If anything, I think this makes nature even more exciting and awesome (in the true sense of the word). That she did so much with so little is stupefying to me.
- dekhn 11y ago
  I would be surprised (I consider terrestrial random origin to be more likely). Ribosomes just turn RNA into protein. Don't forget about DNA and RNA polymerase, which are both very interesting as well. It's really mechanical, but in a way that appeared to happen randomly by evolution, not through design.
jbattle 11y ago
is there any practical approach on the horizon (or here) that allows scientists to apply crispr throughout all the cells in a living organism? I get how this works with a single cell, but typically that's only useful for either very very very small or very very very young individuals (right?)
- zardo 11y ago
  You don't necessarily need to hit every cell in an organism to produce useful therapies. Most cells aren't going to be expressing the gene that's causing a disease, only cells in the affected tissue or organ need to be treated. In some cases, you may not even need to get all of the affected cells, just repairing a subset could improve outcomes. (1/8 of a functioning pancreas is a lot better than 0/8)
- dnautics 11y ago
  No. For permanent genomic changes you have to select what you want. For precise edits, there's usually a counterselection (so it takes two hits). The efficiency of the process is still low. You have to be willing to throw away a lot of cells to get precisely the correct one. One way to think of it is a big component of what CRISPR does is to make it easier to find the good edits (although it does also make good edits more likely).
bcheung 11y ago
I've been studying biochem as a hobby and have been hearing CRISPR off and on but never really heard a good explanation until now. I don't fully understand everything that was said but at least I have a general picture of going on. Thanks for writing this.
NN88 11y ago
This will win the Nobel
panic 11y ago
(Unfortunately, it seems like there is some debate over who invented CRISPR and should be awarded the patent for it.) Maybe the bacterium which first expressed a CRISPR sequence should be awarded the patent. We're just using the tools that nature invented for us!
- tstactplsignore 11y ago
  Truly- When asked why he did not patent the polio vaccine, Jonas Salk responded by asking if you could patent the sun- it seems as though if the sun were discovered today, we'd have a legal battle over all of the attempts to do so.
  - kirsebaer 11y ago
    > “When Jonas Salk asked rhetorically “Would you patent the sun?” during his famous television interview with Edward R. Murrow, he did not mention that the lawyers from the National Foundation for Infantile Paralysis had looked into patenting the Salk Vaccine and concluded that it could not be patented because of prior art – that it would not be considered a patentable invention by standards of the day. http://www.biotech-now.org/public-policy/patently-biotech/2012/01/the-real-reason-why-salk-refused-to-patent-the-polio-vaccine-a-myth-in-the-making http://www.biotech-now.org/public-policy/patently-biotech/20... > In the decades since, a great myth has grown to dominate the popular imagination. Its name is “The Conquest of Polio,” and Salk is its hero.... This retelling of the history of polio, however, is largely a distortion. The full, true story is far more complex. Its hero is Albert Sabin – for if any one man conquered polio, it was Sabin, who developed the oral attenuated live-virus vaccine. While Salk’s vaccine did slow down the incidence of polio among middle-class Americans, its cost and its requirement of three injections and a booster meant that for years the disease continued to affect the poor and others lacking access to proper medical care. It was only after Sabin’s oral vaccine, which was cheap, effective, and easy to administer, was licensed for production in 1962 that polio could be fully controlled in the United States. http://www.technologyreview.com/review/404390/the-myth-of-jonas-salk/ http://www.technologyreview.com/review/404390/the-myth-of-jo...
    - 11y ago
dnautics 11y ago
I think this explanation is missing the real explanation of why CRISPR is useful. I want to take a crack at it. Let's say we want to change in the genome the sequence (where each of the 'letters' represents a somewhat long stretch of base pairs): ABCDE to ABC'DE you would normally create the sequence BC'D in vitro and put it into the cells. The organisms contain mechanisms to match the B & D sections and thus 'swap out' the C section for the C' section. Note that C could be "" which would make the process a straight insertion. C' could be "" which would make the process a straight deletion. C and C' could be a single base pair, which would mimic a point mutation, etc... However, you don't have TOTAL control over this process, it's stochastic, and doesn't have 100% efficiency. So you have to do something clever to make sure you have what you want. Typically that involves inserting resistance to a chemical factor (e.g. antibiotic). So for insertions (if you don't mind a dirty insertion) it's fine, but for other transformations like mutations and deletions, you might have to be clever, and say, do C -> C' -> C'' where the C' includes the selection factor. And C'' is chosen either because it lacks a toxic factor that we put in alongside C' or by doing a reverse selection where we pick clones and test to see if they die (and keep some of the originals in case they pass the test). This process generally works quite well in most microbes with small genomes (E. coli requires a tweak to the process). It is basically effortless with yeast. With higher eukaryotes it's not quite so simple. A competing process is inserting the BC'D sequence elsewhere in the genome. It's not entirely clear why this is such a huge problem, but likely it's because of the increasing complexity and size of the genome. If C' contains a selectable marker, it becomes difficult to distinguish between what you want (ABC'DE) and just BC'D somewhere random in your genome. Both are resistant. And the process becomes bogged down by the need to isolate single cells, propagate them, and check to see if your strain has the substitution you want (relative easy, just a PCR reaction) and no other substitutions elsewhere in the genome (haaaaaaard). The CRISPR advantage is that just before you add BC'D to your cell you create a scission somewhere in C so you're left with ABc//cDE - and what this does is triggers the cell repair system to search for B & D sequences to hook into. Naturally it will find BC'D. Well, if it doesnt, usually a fragmented chromosome will also result in death of the cell, so you're virtually guaranteed that the surviving cells have ABC'DE. With this, the rate of successful targetting so exceeds the rate of random insertion that the necessity to check is basically eliminated (or at least you don't have to search through so many clones to pull out a total success). The net effect is that for many higher organisms genetic manipulation becomes much much much easier. YMM(still)V with some plants which have high level of repeats within the genome.
iaw 11y ago
This actually raised an interesting thought to mind about the long-term ethical implications of lowering the barrier to entry for genetic engineering. What happens when anyone with a little know-how and $10K can use the techniques?
- kanzure 11y ago
  > This actually raised an interesting thought to mind about the long-term ethical implications of lowering the barrier to entry for genetic engineering. What happens when anyone with a little know-how and $10K can use the techniques? The barrier to entry for genetic engineering is already zero; but it has much less sexy names like "washing your hands" and "sex". DNA synthesis is just a matter of being more specific and deliberate about which biological organisms you keep around. Anyone is capable of selectively breeding bacteria, fungi, molds, or anything else. I think the reverse(?) question needs to be asked as well, which is what are the ethical implications of trying to restrict the ability to make DNA? Here's some infotainment I guess: http://diyhpl.us/wiki/diybio/faq/news/ http://diyhpl.us/wiki/diybio/faq/news/
  - iaw 11y ago
    I should have been more specific, when I said 'genetic engineering' I was referring to using techniques like CRISPR to perform gene modifications in animals and humans. No one with the resources required currently would surreptitiously test a new gene on another human, what happens when the resource and knowledge barrier drop?
- george88b 11y ago
  There is a startup that runs genetic engineering experiments for you "in the cloud": https://www.arcturus.io/ https://www.arcturus.io/

108 points by PieSquared 11y ago

ProAm 11y ago

Great podcast on CRISPR from radiolab [1] [1] http://www.radiolab.org/story/antibodies-part-1-crispr/ http://www.radiolab.org/story/antibodies-part-1-crispr/

cheapsteak 11y ago
One of the main arguments given against splicing human embryos on there was that embryos couldn't decide for itself whether it wanted it. I think that's kind of absurd. The decision that impacts it the most has already been made for it - existence. If we take the Buddha's view that life is suffering, then it has been decided that is suffers. Compared to that, what sin is it to give it whatever advantages a few spliced genes can offer?

avinashv 11y ago

While the author is pretty clear that "only a passing knowledge of modern microbiology" is necessary, I think that understates some of the technical language in here. I really laughed at the line, "Silencing a gene with CRISPR/Cas is incredibly simple." Still, I learned a lot. This is the closest I've come to feeling like I know what's going on in CRISPR. CRISPR has got to be one of the most important scientific achievements of the past few decades, right?

DaveWalk 11y ago
Absolutely. The movement from discovery (from the unsexiest of all fields, bacteriology!) to a reliable tool is unprecedented[1] in the scientific realm. For my money it is easily on track for a Nobel Prize: it allows mankind to examine with precision unknown just years before. [1] I see a parallel to short hairpin RNA gene silencing (shRNA, a.k.a. RNA interference, RNAi). A breakthrough discovery, at use at the bench in less then a decade, and an easy clinch for the Nobel Prize. CRISPR has gone even faster.
- dnautics 11y ago
  > The movement from discovery (from the unsexiest of all fields, bacteriology!) to a reliable tool is unprecedented. Uhm, restriction enzymes? for the uninitiated: https://en.wikipedia.org/wiki/Restriction_enzyme https://en.wikipedia.org/wiki/Restriction_enzyme (basically, restriction enzymes are what CRISPR is basically set to replace for complex systems/organisms where restriction enzymes are too weak; although for simple systems restriction enzymes are waaay simpler)
  - dluan 11y ago
    I really wonder if it's just a matter of time before you get clans of technology in bio. Akin to the PHP vs Ruby vs Node vs Go evolution. At the end of the day, they are just tools, and tools however technically shiny, don't by themselves deliver better end products.
    - dnautics 11y ago
      That's already happened with NG DNA assembly. PIPES cloning vs. Gibson Assembly vs. ColdFusion, etc. In the case of restriction enzymes, though, they've been around in continuous use since something like the 70s, they're very well characterized, NEB has had a continuous research program where they've been optimized out the wazoo. Technically speaking they are fundamentally simpler than CRISPR (one component, vs. 2). They also are more generally useful when your genetic manipulation is done outside the cell. So there's a clear tooling difference in CRISPR/RE. Most people who use CRISPR, will use REs in the process of make the DNA piece they're putting in alongside the CRISPR. You'd be a fool to use CRISPR in E. Coli or Yeast. So 'clan'ing ain't gonna really happen here.
neuronic 11y ago
Yes. The next time some "What is the most promising technology?" thread pops up on reddit, you can safely post CRISPR. Depending on how things go with the patent stuff and the technology itself, sooner or later this will absolutely transform our lives. We are looking at the incubation of a technology that may easily save millions of lives (over a long time frame). Potential for misuse is near infinite though - imagine a privatized CRISPR inaccessible to the sub-$50 million/ year crowd. The limitations of CRISPR really do appear to be few though. Lots of techniques and methods will be developed and figured out in the next years. It allows us near complete control over the most essential biology. And all that in vivo. The road ahead is rough but I am confident that CRISPR can become the magic tool I just described. It will be black and white magic. Question is which will dominate?
- zardo 11y ago
  Potential for misuse is near infinite though - imagine a privatized CRISPR inaccessible to the sub-$50 million/ year crowd. I can imagine a lot worse than that. Imagine genetic engineering gets dirt cheap, and that does seem to be the direction we're headed. Novel pathogens are going to be a lot easier to design than treatments and preventative measures to protect against them. How do you stop the proliferation of bio-weapons? I'm thinking that would be about as easy as stopping the proliferation of malware.
  - technotony 11y ago
    One major difference is that you have to order your DNA typically from a third party provider and they can screen for pathogenic sequences. We could probably stop malware if we could screen all the code before anyone was allowed to run it. I think the current system is reasonably robust for stopping novel syn bio pathogens. In my mind the big risk comes with home based DNA printers. There are several close to getting to market (eg http://www.kilobaser.com/ http://www.kilobaser.com/), at that point we lose control over what gets printed and then maybe there are concerns... though I do think creating a pathogen is really hard and most likely to end up killing the creator before anyone else.
    - 11y ago

dperfect 11y ago

Can someone help me understand the main differences between CRISPR and traditional genetic engineering that has been done for many years now? My understanding is that we've had technologies to selectively modify DNA for some time, but perhaps it hasn't been as targeted or reliable as CRISPR? One thing that stands out to me (especially from the radiolab episode) is that it sounds like CRISPR isn't just gene editing in the sense of engineering something in a lab; it's gene editing in an already living organism. If DNA is anything like an organism's "source code", once the code is "shipped" (organism is conceived), traditionally we tend to think of that code as being locked/frozen. It sounds like CRISPR is akin to modifying the code live - "in production", so to speak. Is that a fair analogy? Edit: to explain, when I say "in an already living organism", I'm referring mostly to a developed, multi-celled organism. I understand that traditional techniques also use living cells, but the radiolab episode makes it sound as if a full-grown adult human may someday get a live "DNA upgrade" - at least to applicable portions of the body - via CRISPR, e.g. to remove a genetic predisposition for developing a particular disease. To me, that would be substantially different (in practical application) from genetically engineering something like a gamete or a single-celled bacteria.

cgearhart 11y ago
CRISPR performs pattern matching on the DNA sequence immediately preceding the cut location where new sequences are added. While we have had CTRL-X and CTRL-V for awhile (in the other gene modification techniques you alluded to) CRISPR provides a cursor that allows us to precisely control where the CTRL-V takes place. As for updating "live" code...that's a flawed, but not completely wrong analogy. Other techniques do rely on modifying the genome before "production", and in that sense CRISPR does enable us to edit DNA in cases that would have been impractical before, but it still basically requires performing the modification on each cell individually -- so there are still practical limits on deploying the technique.
- eggie 11y ago
  Precise targeting of genomic cuts has been possible for some time, but more expensive: https://en.wikipedia.org/wiki/Zinc_finger_nuclease https://en.wikipedia.org/wiki/Zinc_finger_nuclease https://en.wikipedia.org/wiki/Transcription_activator-like_effector_nuclease https://en.wikipedia.org/wiki/Transcription_activator-like_e...

deleted 11y ago

[deleted]

brock_r 11y ago

Will anyone here be really surprised if it turns out ribosomes are duplicating machines designed by some alien race? The entire process of reading the DNA code and turning it into proteins is just amazing.

Balgair 11y ago
I understand the downvotes, but the wonder here with biology that the OP has is well placed. I came into bio from DoD/Physics and am constantly astounded by what nature has made. I mean, it's been ~4 billion years and the generation to generation time is ~20 minutes (~1.1E14 generations total), so I think we all can expect a fair bit from nature, but still, she is really clever. I do think about this as well. The complexity, the reliability, the ability for nature to do what she does even in the face of all the thermal noise and viruses and enviroment, it really seems like there must be someone making it happen. Alas, no though! As far as we can tell, it's all just evolution and chance on a planet wide stage with microscopic actors. If anything, I think this makes nature even more exciting and awesome (in the true sense of the word). That she did so much with so little is stupefying to me.
dekhn 11y ago
I would be surprised (I consider terrestrial random origin to be more likely). Ribosomes just turn RNA into protein. Don't forget about DNA and RNA polymerase, which are both very interesting as well. It's really mechanical, but in a way that appeared to happen randomly by evolution, not through design.

jbattle 11y ago

is there any practical approach on the horizon (or here) that allows scientists to apply crispr throughout all the cells in a living organism? I get how this works with a single cell, but typically that's only useful for either very very very small or very very very young individuals (right?)

zardo 11y ago
You don't necessarily need to hit every cell in an organism to produce useful therapies. Most cells aren't going to be expressing the gene that's causing a disease, only cells in the affected tissue or organ need to be treated. In some cases, you may not even need to get all of the affected cells, just repairing a subset could improve outcomes. (1/8 of a functioning pancreas is a lot better than 0/8)
dnautics 11y ago
No. For permanent genomic changes you have to select what you want. For precise edits, there's usually a counterselection (so it takes two hits). The efficiency of the process is still low. You have to be willing to throw away a lot of cells to get precisely the correct one. One way to think of it is a big component of what CRISPR does is to make it easier to find the good edits (although it does also make good edits more likely).

bcheung 11y ago

I've been studying biochem as a hobby and have been hearing CRISPR off and on but never really heard a good explanation until now. I don't fully understand everything that was said but at least I have a general picture of going on. Thanks for writing this.

NN88 11y ago

This will win the Nobel

panic 11y ago

(Unfortunately, it seems like there is some debate over who invented CRISPR and should be awarded the patent for it.) Maybe the bacterium which first expressed a CRISPR sequence should be awarded the patent. We're just using the tools that nature invented for us!

tstactplsignore 11y ago
Truly- When asked why he did not patent the polio vaccine, Jonas Salk responded by asking if you could patent the sun- it seems as though if the sun were discovered today, we'd have a legal battle over all of the attempts to do so.
- kirsebaer 11y ago
  > “When Jonas Salk asked rhetorically “Would you patent the sun?” during his famous television interview with Edward R. Murrow, he did not mention that the lawyers from the National Foundation for Infantile Paralysis had looked into patenting the Salk Vaccine and concluded that it could not be patented because of prior art – that it would not be considered a patentable invention by standards of the day. http://www.biotech-now.org/public-policy/patently-biotech/2012/01/the-real-reason-why-salk-refused-to-patent-the-polio-vaccine-a-myth-in-the-making http://www.biotech-now.org/public-policy/patently-biotech/20... > In the decades since, a great myth has grown to dominate the popular imagination. Its name is “The Conquest of Polio,” and Salk is its hero.... This retelling of the history of polio, however, is largely a distortion. The full, true story is far more complex. Its hero is Albert Sabin – for if any one man conquered polio, it was Sabin, who developed the oral attenuated live-virus vaccine. While Salk’s vaccine did slow down the incidence of polio among middle-class Americans, its cost and its requirement of three injections and a booster meant that for years the disease continued to affect the poor and others lacking access to proper medical care. It was only after Sabin’s oral vaccine, which was cheap, effective, and easy to administer, was licensed for production in 1962 that polio could be fully controlled in the United States. http://www.technologyreview.com/review/404390/the-myth-of-jonas-salk/ http://www.technologyreview.com/review/404390/the-myth-of-jo...
  - 11y ago

dnautics 11y ago

I think this explanation is missing the real explanation of why CRISPR is useful. I want to take a crack at it. Let's say we want to change in the genome the sequence (where each of the 'letters' represents a somewhat long stretch of base pairs): ABCDE to ABC'DE you would normally create the sequence BC'D in vitro and put it into the cells. The organisms contain mechanisms to match the B & D sections and thus 'swap out' the C section for the C' section. Note that C could be "" which would make the process a straight insertion. C' could be "" which would make the process a straight deletion. C and C' could be a single base pair, which would mimic a point mutation, etc... However, you don't have TOTAL control over this process, it's stochastic, and doesn't have 100% efficiency. So you have to do something clever to make sure you have what you want. Typically that involves inserting resistance to a chemical factor (e.g. antibiotic). So for insertions (if you don't mind a dirty insertion) it's fine, but for other transformations like mutations and deletions, you might have to be clever, and say, do C -> C' -> C'' where the C' includes the selection factor. And C'' is chosen either because it lacks a toxic factor that we put in alongside C' or by doing a reverse selection where we pick clones and test to see if they die (and keep some of the originals in case they pass the test). This process generally works quite well in most microbes with small genomes (E. coli requires a tweak to the process). It is basically effortless with yeast. With higher eukaryotes it's not quite so simple. A competing process is inserting the BC'D sequence elsewhere in the genome. It's not entirely clear why this is such a huge problem, but likely it's because of the increasing complexity and size of the genome. If C' contains a selectable marker, it becomes difficult to distinguish between what you want (ABC'DE) and just BC'D somewhere random in your genome. Both are resistant. And the process becomes bogged down by the need to isolate single cells, propagate them, and check to see if your strain has the substitution you want (relative easy, just a PCR reaction) and no other substitutions elsewhere in the genome (haaaaaaard). The CRISPR advantage is that just before you add BC'D to your cell you create a scission somewhere in C so you're left with ABc//cDE - and what this does is triggers the cell repair system to search for B & D sequences to hook into. Naturally it will find BC'D. Well, if it doesnt, usually a fragmented chromosome will also result in death of the cell, so you're virtually guaranteed that the surviving cells have ABC'DE. With this, the rate of successful targetting so exceeds the rate of random insertion that the necessity to check is basically eliminated (or at least you don't have to search through so many clones to pull out a total success). The net effect is that for many higher organisms genetic manipulation becomes much much much easier. YMM(still)V with some plants which have high level of repeats within the genome.

iaw 11y ago

This actually raised an interesting thought to mind about the long-term ethical implications of lowering the barrier to entry for genetic engineering. What happens when anyone with a little know-how and $10K can use the techniques?

kanzure 11y ago
> This actually raised an interesting thought to mind about the long-term ethical implications of lowering the barrier to entry for genetic engineering. What happens when anyone with a little know-how and $10K can use the techniques? The barrier to entry for genetic engineering is already zero; but it has much less sexy names like "washing your hands" and "sex". DNA synthesis is just a matter of being more specific and deliberate about which biological organisms you keep around. Anyone is capable of selectively breeding bacteria, fungi, molds, or anything else. I think the reverse(?) question needs to be asked as well, which is what are the ethical implications of trying to restrict the ability to make DNA? Here's some infotainment I guess: http://diyhpl.us/wiki/diybio/faq/news/ http://diyhpl.us/wiki/diybio/faq/news/
- iaw 11y ago
  I should have been more specific, when I said 'genetic engineering' I was referring to using techniques like CRISPR to perform gene modifications in animals and humans. No one with the resources required currently would surreptitiously test a new gene on another human, what happens when the resource and knowledge barrier drop?
george88b 11y ago
There is a startup that runs genetic engineering experiments for you "in the cloud": https://www.arcturus.io/ https://www.arcturus.io/