Gene Drives: How to Genetically Modify an Ecosystem

In summary, scientists have discovered a way to create gene drives that can drastically increase the chances of a gene being passed on to offspring. This technology has potential applications in modifying mosquito populations to prevent malaria, managing agricultural pests and weeds, and limiting the damage of invasive species. However, there are concerns about the potential consequences of introducing these modified genes into wild populations. Two recent studies have demonstrated the effectiveness of gene drive technologies in fruit flies and yeast, using the CRISPR/Cas9 system. There are ongoing debates about the regulation and ethical implications of this research, as it has the potential to make significant changes to our environment.
  • #1
Ygggdrasil
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Genes normally have a 50-50 chance of being passed from parent to offspring, but scientists may have figured out a way to create gene drives that show up in offspring with a much higher frequency:
One type of gene drive influences inheritance by copying itself onto chromosomes that previously lacked it. When an organism inherits such a gene drive from only one parent, it makes a cut in the chromosome from the other parent, forcing the cell to copy the inheritance-biasing gene drive—and any adjacent genes—when it repairs the damage.
(http://blogs.scientificamerican.com...chnologies-wont-lead-designer-babies/']crispr-could-revolutionize-ecosystem-management/[/url])

This idea had been discussed for a while (it was first proposed by Austin Burt in 2003), but new gene editing methods developed in the past few years seem to make this idea much closer to reality.

What is most exciting – and concerning – about gene drive technology is that when introduced into wild populations, organisms containing gene drives would breed with the population and could spreading the modified genes throughout the population even if the modifications decrease the reproductive fitness of the organism. The researchers imagine this technology could have a number of applications, for example, modifying mosquito populations to prevent the spread of malaria, modifying agricultural pests and weeds to deal with pesticide and herbicide resistance, and modifying invasive species to limit their ecological damage. A recent paper in the journal eLife discusses how such gene drives could be engineered and their potential applications.

However, with such far reaching consequences, society should approach this technology with caution, and the same authors of the eLife paper have also published a policy forum paper in Science opening the conversation about how this technology should be regulated.

In addition to the Scientific American blog post linked above, PBS also has a good, popular press summary of the papers: http://www.pbs.org/wgbh/nova/next/e...chnologies-wont-lead-designer-babies/']crispr-gene-drives/[/url]
 
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Biology news on Phys.org
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Two studies published today provide experimental demonstration of gene drive technologies in fruit flies and yeast (two commonly used experimental organisms in biology). Both these studies make use of https://www.physicsforums.com/threads/breakthrough-prize-genome-editing-with-https://www.physicsforums.com/insights/dont-fear-crispr-new-gene-editing-technologies-wont-lead-designer-babies/-cas9.798959/. Here's an exerpt from a news article in Science:

In a study published online this week, researchers describe a technique for creating mutations that invade the genome and transmit themselves across to the next generation with near 100% success, defying the classic laws of Mendelian genetics. It is the latest—and some say, most impressive—example of gene drive: biasing inheritance to spread a gene rapidly through a population, or even an entire species. At this level of efficiency, a single mosquito equipped with a parasite-blocking (it blocks transmission, doesn't kill the parasites) gene could in theory spread malaria resistance through an entire breeding population in a single season. A collaboration is under way, based on this study, to do just that.
(http://news.sciencemag.org/biology/2015/03/chain-reaction-spreads-gene-through-insects)

Here are the studies:
Gantz and Bier. The mutagenic chain reaction: A method for converting heterozygous to homozygous mutations. Science. Published online March 19, 2015. doI:10.1126/science.aaa5945
DiCarlo et al. RNA-guided gene drives can efficiently and reversibly bias inheritance in wild yeast. bioRxiv, posted March 19, 2015. doi:10.1101/013896 (this was posted in the non-peer reviewed bioRxiv pre-print server, but it comes from a reputable group with expertise in the area)

These studies have stirred much debate among scientists because they are capable of making large scale changes to our environment. Both groups employed safeguards in their research to prevent accidental release of their technologies into their environment, but the barrier to creating gene drives is not very high, and many research groups around the world likely have the capabilities to build similar systems. What sorts of restrictions should we place on this type of research? Should systems like these be used in the wild to, for example, combat malaria, and what criteria should we use to make that determination?
 
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  • #4
A very interesting report.

Sounds like something that would spread so incredibly fast that I wonder why it has not occurred naturally at some point, or at least why it is not so common we see it today.

If I understand the method correctly, you need a specific CRISPR complex for a specific gene you want to spread? And then you also need one gene for this specific CRISPR complex - and that has to spread faster as well?
 
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  • #5
mfb said:
If I understand the method correctly, you need a specific CRISPR complex for a specific gene you want to spread? And then you also need one gene for this specific CRISPR complex - and that has to spread faster as well?
Here's a diagram from the Science paper describing how it works:

9d4f6123-02cd-476f-98a4-739d00fe4cf8_zpswec0rdco.jpg

CRISPR/Cas9 is a complex between a protein called Cas9 and an RNA containing specific structural features that allow it to bind to Cas9 (called the guide RNA or gRNA). A specific part of the gRNA sequence tells the Cas9 protein which sequences to cut, and by changing that sequence in the gRNA, researchers can "program" CRISPR/Cas9 to a specific sequence of DNA. When CRISPR/Cas9 cuts the DNA on one chromosome, it activates the DNA repair pathways in the cell. These DNA repair pathways grab the homologous chromosome (remember, we have two copies of each chromosome), finds a region with a similar sequence to the damaged region, then copies the sequence from the homologous chromosome onto the damaged chromosome. So, everything between the two homology arms of the gene drive (HA1 & HA2 in the figure), which would include the Cas9 gene, the gRNA, and whatever else you include, gets copied onto the other chromosome. Thus, the Cas9, gRNA, and other additional sequences all spread together.

You would need a specific gRNA for each specific gene you would want to spread, but the same Cas9 works for any gRNA. The study done in yeast by George Church's lab made a gene drive containing only the homology arms, the gRNA, and the target gene they wanted to spread. They supplied the Cas9 in a separate plasmid so that they could better control the process.

Sounds like something that would spread so incredibly fast that I wonder why it has not been occurred naturally at some point, or at least why it is not so common we see it today.
That's a good question. The CRISPR/Cas9 system comes from bacteria and these bacteria control the system such that it does not target the bacterium's own DNA (it acts as a defense against viral DNA), so potentially these things have never popped up in eukaryotes (which have the homologous repair system that helps to copy gene drives).
 
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  • #7
Filip Larsen said:
issues that this technology raises

Runaway diversity scares me. 12 new viruses this year 144 next year perhaps 20,000 the year after? To introduce a new ecosystem which could devastate the one that exists just sounds risky right off the bat. Especially one based on mass mutation of species.
 
  • #8
I think how fast it would spread depends at least in part on the gene(s) in question. If they gene harms the organism to much it won't be able to pass it on, and there is also http://evolution.berkeley.edu/evosite/evo101/IIIE3Sexualselection.shtml [Broken] to think about.
 
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  • #9
But it still seems it could spread even if it confers a sgnificant disadvantage (within limits). Prsumably that s what makes it attractive as a weapon against some mosquitoes and such, but also it sounds potentially disastrous especially if it finds a way to cross species some time after having been released in the wild. Scary stuff,
 
  • #10
This could also be used in eugenics in humans ? In this case it is really a thing to avoid
 
  • #11
jk22 said:
This could also be used in eugenics in humans ? In this case it is really a thing to avoid

The http://blogs.scientificamerican.com/guest-blog/2014/07/17/gene-drives-https://www.physicsforums.com/insights/dont-fear-crispr-new-gene-editing-technologies-wont-lead-designer-babies/-could-revolutionize-ecosystem-management/ piece addresses this question:
gene drives require many generations to spread. We could alter entire populations of fast-reproducing insects in a couple of years—depending on how many we release—but it would take decades or centuries for long-lived organisms. That’s why gene drives won’t be able to affect human populations without taking centuries. They’re also easily detected by genome sequencing and can’t spread accidentally through populations in which mate choice is artificially controlled, which greatly limits their potential to affect crops and domesticated species.

While gene drives aren't likely going to affect humans, the CRISPR/Cas9 technology is currently being used by various research groups to http://www.technologyreview.com/featuredstory/535661/engineering-the-perfect-baby/. Science is even reporting that a paper demonstrating gene editing in human embryos has already been submitted for publication (although genetic engineering of human embryos is banned in many countries, it is legal in some major countries like the US and China). So, technologies to create heritable changes in the human genome currently exist and are accessible to many groups around the world. The danger, of course, that is we still don't understand enough about the biology of the human genome to know which genes to edit in order to alter many of the traits we care about (like intelligence).
 
  • #12
The direct risk from human genetical engineering doesn't seem the most concerning. But spreading it into the wild...
And it's not very reassuring to hear "don't worry, it would take centuries"
 
  • #13
Seems a good time to apply the progressive's favorite, The Precautionary Principle.
 
  • #14
Maybe the prophecy of the brave new world is not far away. Already with those techniques ips and cloning males are not needed anymore for reproduction, technically ? But psychologically maybe couples are still needed, like a duality principle.
 
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  • #15
jk22 said:
This could also be used in eugenics in humans ? In this case it is really a thing to avoid

Why? Ever known someone with Huntington’s or Duchenne's?

Fact is, every animal that mates is deeply concerned with the genetic card they will deal their offspring. Humans are also extremely obsessed by this. It is all eugetics, albeit a terrible crude form.

We are humans because of our genes. We should treasure the quality of the human gene pool highly. CRISPR will help us improve the human gene pool. So no more need for children to die horrible deaths or people to be rejected because they are too ugly to mate with.

It is unethical to put people on a plane that isn't tested, fixed, and found to be safe. Same will soon be true for bearing children with unedited genomes.

In fact, looking at my personal decision, I think it would already be immoral for me to have children without paying the 500 euro to have my genome checked. And if it comes out bad, I may be forced by ethics to not have children. Even if it means I have to be lonely and without family the last 10 years of my life.Every child has the right to a set of genes that make a normal life possible. Just as every child has the right to get vaccinated. If the parents disagree, the child should be protected from the parents.
I am glad I am not in the position where I have to decide on mandatory sterilization, decide on whose indivisible right is to be violated in favour of upholding the other. Let's hope CRISP works really well asap.We have a moral obligation here to future generations.
 
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  • #16
It is not genetics but a more global aspect : The thing is that those methods remain expensive and hence like wealth health go to the richer there is no democratization process going on, it is a kind of peculiar.

For example i have schizophrenia and at the beginning my parents felt guilty but with the time they disculpabilized and there remain the nature that human won't be able to control. Now for physical disease it could be a good thing but there most of the time remains randomness with genetics.
 
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  • #17
@Almeisan, the position you express is very strong and not uncontroversial.
 
  • #18
Almeisan said:
In fact, looking at my personal decision, I think it would already be immoral for me to have children without paying the 500 euro to have my genome checked. And if it comes out bad, I may be forced by ethics to not have children. Even if it means I have to be lonely and without family the last 10 years of my life.

This is quite a dangerous way of looking at things. For example, how do you define "bad"?

A recent study published in http://dx.doi.org/10.1038/ng.3243[/URL] sequenced the genomes of 2000 individuals, and found that 7.7% harbored at least one gene in which both copies carried loss-of-function mutations. This study revealed [url=http://news.sciencemag.org/biology/2015/03/one-thousand-genes-you-could-live-without]~1,000 genes seemed like they could be knocked out completely without any major adverse health effects[/url] (though, research is continuing on those individuals to see if they can find any effects, especially since some of those genes were, in fact, thought to be important). There are also documented cases where knocking out particular genes seems to be beneficial (see the case of [url=http://www.nature.com/news/genetics-a-gene-of-rare-effect-1.12773]PCSK9[/url]).

The point here is that, if one were to sequence your genome, it is very likely that one would find many "errors" in the genome. In the vast majority of cases, however, we wouldn't know if these "errors" we identify would have any major functional consequences. Certainly, screening for known genetic disorders is important, but there's a lot of grey area in defining a genetic disorder (for example, would an allele that slightly increases one's risk of type II diabetes be considered a genetic disorder?).

Furthermore, as we perform more studies that try to identify the genes associated with particular traits, we're quickly finding that, even for traits are very heritable like height, no one gene has a major effect on the trait. Rather, the trait is controlled by hundreds of genes that all have very small effects. This throws into question whether it would even be possible to alter traits like height or intelligence without whole-scale re-writing of the genome (something not possible without major breakthroughs in gene editing technology).
 
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  • #19
All you are saying is that we might not know right now what is good and what is bad? That's all besides the point.

I don't know what you mean with 'errors'. For many diseases, we know very well what the ΔF508 mutation is, how the defective protein turns out, and that this is the cause of the disease. Are you really saying that undoing the 3 base pair mutation for, say cystic fibrosis, giving the patient suffering from the symptoms the allele that 29 in 30 of the people have, who seem to have perfectly fine functioning CFTR, would cause even worse symptoms?
All you have to do is give a patient the healthy allele of one of the parents, one she or he would have gotten anyway if not for the bad luck.Are you really saying ordinary 'healthy alleles' cause more disease than 'diseased alleles'? You can't see the difference between starting with fixing the most heinous and obvious genetic diseases? So we can't start out to cure the most cruel genetic diseases without also tweaking everything else that we shouldn't be touching yet?

I don't know why you introduce height or introduce traits that aren't coded for by alleles. Many of these diseases are the result of a defective protein. Genes code for proteins. It can't be more obvious. In some cases we in fact already provide the patient with medicine containing the correct protein.
There isn't a protein that is the sole determining factor for your height. Also, the natural variation in height, as opposed to a growth disorder, isn't something that requires medical treatment.

It's not like you are giving an example of a gene that has a 5% odds to cause cancer before age 45, but is also correlated with brain function(and might make people smarter/nicer/more social, though we have no way to know). It's not like I am saying we should cut everything suspicious out of our genome and risk actually making it worse, not better. The whole debate is the argument that we should let nature run it's course, as intended.All pharmaceuticals have side-effects. Often very severe ones. We still use them. Are you in opposition against this as well? Fixing the gene itself, when correctly identified and correctly replaced, has zero side-effects. CRISPR so far seems extremely selective. Of course CRISPR should meet all the standards we put on medical treatments right now. But I doubt you think I say CRISPR should get a special treatment.

You quote all these articles to look cool, but you seem not to know what there relevance might be, if any.
I don't see how apparently defective proteins that don't seem to cause any disease have any relevance. I am also not saying that by tomorrow we should insert genes for endocellulase or daptomycin or something.

And yes, the idea that some genes in our genome can potentially code for proteins that only do us harm, may be true. Only more reason to look for them, not less.
Of course many genes are going to have tradeoffs. But even there CRISPR can give a solution. You can knock out cancer-causing heart-disease inhibiting genes in certain people, do the opposite in others, until a long-term solution is found.
 
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  • #20
Almeisan said:
You can't see the difference between starting with fixing the most heinous and obvious genetic diseases? So we can't start out to cure the most cruel genetic diseases without also tweaking everything else that we shouldn't be touching yet?

Sure, I would agree with this, though the line one draws between the most cruel genetic diseases and ones that should not be touched yet can be somewhat fuzzy. Diseases like cystic fibrosis, Huntington's disease, and sickle cell anemia are good examples. What about gene variants that confer disease risk? BRCA1 and BRCA2 mutations, TP53 mutations, and other mutations that confer high risk of developing cancer would probably be a good idea. But, scientists have identified numerous mutations that seem to be associated with cancers of some type and many other diseases, but often the size of the risk and the penetrance of the phenotype is unclear. This is probably an example of letting the perfect be the enemy of the good, and a slippery slope fallacy, but these are important questions that should be addressed.

Furthermore, for most of the high risk genetic disorder that we'd like to fix are Mendelian, so these could be avoided through preimplantation genetic diagnosis of embryos rather than gene editing which currently carries some risks of introducing unintended genetic changes elsewhere in the genome. In this case, one could make the argument that this fact makes germline gene editing unethical because there are safer alternatives available that could achieve the similar goals.

Overall, I agree with your points more than I disagree and am mainly bringing up these points as more of a devil's advocate.
 
  • #21
This discussion reminds me of the movie Gattaca. At any rate one potential issue with genetically modifying people is prejudice. Look at the way some people respond to genetically altered crops. It's a little worrisome to think how they might respond to genetically modified humans. Even if the genetic modification is only to fix a genetic disease.
 
  • #22
Evanish said:
This discussion reminds me of the movie Gattaca. At any rate one potential issue with genetically modifying people is prejudice. Look at the way some people respond to genetically altered crops. It's a little worrisome to think how they might respond to genetically modified humans. Even if the genetic modification is only to fix a genetic disease.

Well, the problem I have is not with the fact that the crops have been genetically modified, but with the fact that we do not know the
possible consequences of that change. I would just prefer that some testing be done before allowing the GMOs into the marketplace.
Ditto for humans; you are tampering with something you do not fully understand, and you cannot control all the consequences of what
you are doing. Just slow down and do things carefully.
 
  • #23
I can see how you test food from genetically modified plants, but how do you test genetic modifications in the human genome? Test results from other animal species might be interesting, but you'll never get conclusive results from that alone.
 
  • #24
mfb said:
I can see how you test food from genetically modified plants, but how do you test genetic modifications in the human genome? Test results from other animal species might be interesting, but you'll never get conclusive results from that alone.

Well, you can, e.g., modify one gene at a time, maybe start with "relatively unimportant" genes, see what happens and use that as data to go onto more ambitious changes.
 
  • #25
WWGD said:
I would just prefer that some testing be done before allowing the GMOs into the marketplace.

GMOs are tested quite extensively before being introduced into the marketplace (see http://www.fda.gov/Food/FoodScienceResearch/Biotechnology/ucm346030.htm [Broken]). Yes, there are problems with the approach, for example, the fact that the company producing GMOs is responsible for performing the testing (mainly b/c no one wants to give the FDA enough money to be able to perform the tests themselves). However, given the companies' financial stakes in GMOs and the public backlash that would ensue if there were problems with their product, it is not a bad solution, and certainly is not a situation where no testing occurs.

mfb said:
I can see how you test food from genetically modified plants, but how do you test genetic modifications in the human genome? Test results from other animal species might be interesting, but you'll never get conclusive results from that alone.

WWGD said:
Well, you can, e.g., modify one gene at a time, maybe start with "relatively unimportant" genes, see what happens and use that as data to go onto more ambitious changes.

mfb brings up an excellent point. Would it ever be ethical to introduce permanent, heritable changes to the genome of an unborn individual when you don't know the effects of such changes?
 
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  • #26
What would be more unethical? Deliberately let someone be born with a Duchenne allele. Or let that same person be born with a functioning gene coding for a functioning dystrophin protein, but not knowing very well if the treatment may have some effect or something may be overlooked?

Don't we do clinical trials and tests on animals right now? I don't see how you can say we can't make inferences from animals. (ignoring how immoral it may or may not be). But these proteins aren't unique to humans. We can put disease causing allales in animals for almost all these well-known genetic diseases and it should cause very similar symptoms. This is being done right now by quite a few teams.
Also, there will be human volunteers.

If you carry this line for all medicine, we wouldn't even be allowed to use antibiotics or vaccins. In fact, there's still people arguing against vaccination.Each year many people outright die from normal everyday pharmaceuticals. We never really know all the systems we are tuning or affecting when introducing a substance. Be it corticosteroids, statins, birth control, painkillers, etc. Let's not even get started on the central nervous system.

I suspect that when CRISPR is reliable, and it has all the promise to be so, it will be one of the treatments with the least side-effects. Because you are never tinkering with gene expression. All you are doing is fixing a mutation that completely breaks a protein. Often a point mutation resulting in a premature stop codon or a frame shift. Often you are changing only 1 basepair.
 
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  • #27
Almeisan said:
What would be more unethical? Deliberately let someone be born with a Duchenne allele. Or let that same person be born with a functioning gene coding for a functioning dystrophin protein, but not knowing very well if the treatment may have some effect or something may be overlooked?

Except in rare cases, you can do this through preimplantation genetic diagnosis (PGD) instead of gene therapy. Scientists are able to perform single cell sequencing on human oocytes or fertilized embryos in order to determine which cells carry the mutation of allele and which ones don't. They can then implant those only those lacking the particular disease alleles. In the example of Duchenne muscular dystrophy (a recessive X-linked trait), this procedure could guarantee that female carriers or males with the disease do not pass the condition down to their children (the one case where gene editing would be necessary is the case of a female carrying two copies of the disease allele, which is very rare).As for the issue of testing, I agree that not much testing would have to be done for fixing disease alleles (other than providing evidence for the general safety of CRISPR/Cas9 gene editing, which is something that could be evaluated in human cell lines before being used in people). However, I argue above that PGD is an easier way of achieving this goal than gene editing. The area where gene editing would be required is in the introduction of new traits (e.g. knockout of PCSK9 for improved cardiovascular health). While we have limited data that such a knockout is safe (there are people lacking functional copies of PCSK9 who seem perfectly healthy), there might be the worry that such mutations are not tolerated in certain genetic backgrounds because of potential interactions of that gene with other genes in the body. For example, there are definitely cases where mutations in two different genes together can cause a disease, where either mutation alone does not cause a problem. It would be challenging to evaluate the potential for such effects in animal studies. Small scale tests in stem cell may be possible, it would be challenging to evaluate gene edits that make changes system-wide (for example, to cholesterol metabolism in the case of PCSK9).
 
  • #28
Ygggdrasil said:
While we have limited data that such a knockout is safe (there are people lacking functional copies of PCSK9 who seem perfectly healthy), there might be the worry that such mutations are not tolerated in certain genetic backgrounds because of potential interactions of that gene with other genes in the body. For example, there are definitely cases where mutations in two different genes together can cause a disease, where either mutation alone does not cause a problem. It would be challenging to evaluate the potential for such effects in animal studies. Small scale tests in stem cell may be possible, it would be challenging to evaluate gene edits that make changes system-wide (for example, to cholesterol metabolism in the case of PCSK9).
This argument has unpleasant implication. If it is unethical to try different combinations of already existing human genes then it seems like someone could argue that interracial marriage is unethical.
 
  • #29
Almeisan said:
Don't we do clinical trials and tests on animals right now? I don't see how you can say we can't make inferences from animals. (ignoring how immoral it may or may not be). But these proteins aren't unique to humans. We can put disease causing allales in animals for almost all these well-known genetic diseases and it should cause very similar symptoms. This is being done right now by quite a few teams.
I don't say you cannot make inferences, but genetic changes in human can have effects different from the effects on other animals.
Also, there will be human volunteers.
For drug testing this is easy, but how can a baby volunteer before it is even born?

Evanish said:
If it is unethical to try different combinations of already existing human genes
Oh, we try that with every child anyway. But I'm sure many will see a large difference between sampling genes at random from two humans, and biochemical modifications. Especially if you go beyond single base pair mutations that are well-known.
 
  • #30
Evanish said:
This argument has unpleasant implication. If it is unethical to try different combinations of already existing human genes then it seems like someone could argue that interracial marriage is unethical.
Since PCSK9 double deletion is very rare, we don't have a lot of data about its effects in a variety of genetic backgrounds, so it is reasonable to have these concerns (whether these concerns should halt potential trials of PCSK9 gene editing is debatable, however). Re-assortment of common variants is less concerning, especially in interracial marriages where there is presumably less chance of similar variants recombining to knock out both copies of a gene.

However, your general point that every natural conception is an experiment is important to keep in mind. Even if gene editing does run into unforeseen problems, the frequency of problems seen in conventionally conceived children is probably the appropriate point of comparison.
 
  • #31
mfb said:
Oh, we try that with every child anyway. But I'm sure many will see a large difference between sampling genes at random from two humans, and biochemical modifications. Especially if you go beyond single base pair mutations that are well-known.

So what is the difference? Besides trying random genes is likely to have a higher risk than deliberately picking them.

That people are going to object with 'we should not play god' or 'slippery slope', I know. But I don't think those are very good reasons to condemn a child to a genetic card with an early death or significant complications/reduced quality of life.
 
  • #32
Almeisan said:
So what is the difference?
Depending on what you do, there might be no difference at all.
That people are going to object with 'we should not play god' or 'slippery slope', I know.
And that is a serious issue. People don't care about ~2 mSv/year of background radiation, they care about the extra 0.0001 mSv from living close to a nuclear power plant. You can collect many signatures if you suggest to ban atoms, genes, or chemicals in general (or just dihydrogen monoxide in particular). Even PGD, where no genes are changed, is disputed.
 
  • #33
An update on gene drive research:

Two groups have recently published papers demonstrating that gene drives work in mosquitoes. One study demonstrated gene drives in Anopheles stephensi, a malaria vector in the Indian subcontinent, and demonstrated that it could be used to spread malaria-resistance genes. The other group worked with Anopheles gambiae, a malaria vector in sub-Saharan Africa, and demonstrated a gene drive that affects female (but not male) fertility and thus could be used to reduce mosquito populations. Links to the studies and a news piece summarizing them are below.

Gantz et al. 2015. Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Anopheles stephensi. Proc Natl Acad Sci USA 112: E6736. doi:10.1073/pnas.1521077112

Hammond et al. 2016. A CRISPR-Cas9 gene drive system targeting female reproduction in the malaria mosquito vector Anopheles gambiae. Nat. Biotech. 34: 78. doi:10.1038/nbt.3439

Summary from Nature news

It's possible that a gene drive targeting female fertility could help against the current Zika virus spread in the Americas by limiting mosquito populations. Of course, the decision to release a gene drive into the wild should not be taken lightly, and research should be done to consider any long-term unintended consequences of such action. Still, with a Zika virus vaccine potentially a decade away, gene drives seem like a solution that could be available in a few years.
 
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1. What is a gene drive?

A gene drive is a genetic engineering technique that allows for the rapid spread of a specific gene throughout a population. This is achieved by modifying the inheritance patterns of the gene, increasing its chances of being passed down to the next generation.

2. How does a gene drive work?

A gene drive works by using a specific type of gene editing tool, such as CRISPR, to introduce a desired gene into an organism's DNA. This gene is designed to be inherited by future generations at a higher rate than normal, resulting in a rapid spread of the gene throughout the population.

3. What is the purpose of using gene drives?

The main purpose of using gene drives is to genetically modify an ecosystem in order to achieve a desired outcome, such as reducing the population of disease-carrying insects or increasing the resistance of a species to a particular threat. It is also being researched as a potential tool for conservation efforts.

4. What are the potential risks of using gene drives?

There are several potential risks associated with using gene drives, including unintended consequences on non-target species, disruption of natural ecosystems, and the potential for the gene drive to spread beyond the intended population. There is also concern about the ethical implications of permanently altering a species' genetic makeup.

5. How are gene drives regulated?

Currently, there is no comprehensive regulation for gene drives, but they are subject to existing regulations for genetic engineering and biotechnology. Some countries have implemented specific policies and guidelines for gene drives, and there are ongoing discussions about the need for international regulations to address the potential risks and ethical concerns.

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