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To those wondering, this does not involve gene splicing or anything like that. Instead, defective mitochondria are being replaced with mitochondria from a heal

by Cogito 12y ago

To those wondering, this does not involve gene splicing or anything like that. Instead, defective mitochondria are being replaced with mitochondria from a healthy donor. This technique is only valid for diseases involving defective mitochondria. The mitochondrial DNA is responsible for very very little of the genetic material that defines who a person is, essentially limited to how effective the mitochondria are at their job. This is around 0.1% of the total genetic code. Mitochondria are organelles in our cells that break down molecules to provide energy for the cell, in the form of ATP. They have their own genetic code completely distinct from the host cell's DNA. The mitochondria are replaced in either the egg OR in the embryo. In both cases this is done by removing the nucleus (containing the cell's genetic material) from the cell that has defective mitochondria and transferring it to a donor cell with healthy mitochondria. The donor cell's nucleus is completely removed. The mitochondrial DNA is passed down from the mother alone, whilst the DNA in the embryo is formed from both the mother and father. For this reason mitochondrial DNA has much less genetic diversity. Mitochondria 'reproduce' by binary fission which is similar to bacterial cell division and produces little variation in its genetic code, whilst egg and sperm go through meiosis allowing the genetic code to be mixed. Opposition seems to be coming from two camps. - Those who don't like the destruction of the donor embryo (when that method is used), - Those who think this is the start of ever more invasive genetic modification of humans, or so called "designer babies"

Crito 12y ago
How do mitochondria replicate their own DNA? Do they somehow have the rest of the cell do it, or do they contain/produce and use all of the necessary enzymes/proteins/base-pairs/etc to do it by themselves? The relationship between them and their host cell almost seems similar to ant-fungus mutualism.
- schoen 12y ago
  This is actually a now-standard theory of the origin of mitochondria (that they were originally separate organisms): https://en.wikipedia.org/wiki/Symbiogenesis https://en.wikipedia.org/wiki/Symbiogenesis
- jforman 12y ago
  All of the DNA replication machinery that operates in mitochondria is encoded in the nucleus, translated in the cytoplasm, and then transported into the mitochondrion: "The remaining ~1500 mitochondrial proteins are encoded in the nucleus, including all proteins needed for replication and expression of the small mtDNA genome (Falkenberg et al., 2007)" from http://ac.els-cdn.com/S0092867409012458/1-s2.0-S0092867409012458-main.pdf?_tid=96f8c212-ac13-11e4-ac6b-00000aacb35e&acdnat=1423016266_587dd8a75f971860b976b3ea016b270f http://ac.els-cdn.com/S0092867409012458/1-s2.0-S009286740901...
gameshot911 12y ago
>Those who think this is the start of ever more invasive genetic modification of humans, or so called "designer babies" Well...this is the start of ever more invasive genetic modification of humans.
- Cogito 12y ago
  I guess it is! That said, I don't think the 'slippery slope' arguments made in parliament are valid, precisely because this is a very specific kind of genetic modification: > "But one thing is for sure, once this alteration has taken place, as someone has said, once the gene is out of the bottle, once these procedures that we're asked to authorise today go ahead, there will be no going back for society." Replacing mitochondria is very different to designing genetic traits, either through careful selection of eggs and embryos, or splicing, and I think that conflating the two is silly. If laws were introduced that would allow modification of the primary genetic material that debate would be had then. This law will not shoo-in laws that provide for that kind of genetic modification.
  - 2muchcoffeeman 12y ago
    The 'slippery slope' argument also seems easy to fix in this case. Can't we just extend whatever laws with the addition of this specific treatment? Anything else has to be looked at on a case by case basis.
    - skore 12y ago
      > Can't we just extend whatever laws with the addition of this specific treatment? Anything else has to be looked at on a case by case basis. Cue people shouting about how politics are slow and killing people while also forcing politicians into making medical judgements that they may not be qualified for, further increasing the chance that they become the playthings of lobbyists who "do their homework for them". I'm utterly divided on this issue by the way, just noting the inevitable discussion that follows your logic.
  - one-more-minute 12y ago
recibe 12y ago
Opposition is also from those who don't think that human reproduction is a moral imperative to be guaranteed by the state - under the fallacy that it somehow increases our collective quality of life. Like me.
- one-more-minute 12y ago
  That's an interesting point, and perhaps a good argument for not diverting public health resources towards this kind of procedure (I'm sure there are good arguments for the opposite, too). But there's a big difference between not actively endorsing a procedure like this and making it illegal.
  - recibe 12y ago
    Not really. This procedure is likely to be inaccessible to the general public without subsidy via insurance (public or private). My argument is that one's ability to reproduce should not be guaranteed by the state, and therefore the state should not create laws that overtly or inadvertently sanction the genetic engineering of eggs or embryos to that end. This law does precisely that.
    - one-more-minute 12y ago
      > one's ability to reproduce should not be guaranteed by the state, and therefore the state should not create laws that overtly or inadvertently sanction ... Ok, but even taking the first part of that as given I don't understand why the second part follows. I don't think one's ability to go on holiday should be guaranteed by the state, either, but that doesn't mean plane travel should be illegal.
      - recibe 12y ago
        From the article: "The method, which was developed in Newcastle, should help women like Sharon Bernardi, from Sunderland, who lost all seven of her children to mitochondrial disease." Reasoning: Sharon Bernardi hasn't been able to reproduce naturally without this "method". But the UK is going to make this method legal - and because its healthcare system is publicly funded the UK government (and thus the public) will also pay for the implementation of the method. This represents an example where the state is making a guarantee - a formal promise or assurance - that it will pay for citizens that normally couldn't have children to be able to have them. From the article: Prime Minister David Cameron said: "We're not playing god here, we're just making sure that two parents who want a healthy baby can have one." What's not logical about that?
tosseraccount 12y ago
"This is around 0.1% of the total genetic code." More like 13% ... check my math ... Most chromosomes have 2 copies per cell. However ... there are many copies of the mitochondria : http://en.wikipedia.org/wiki/Human_mitochondrial_genetics#Quantity http://en.wikipedia.org/wiki/Human_mitochondrial_genetics#Qu... <i> Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500.</i> Mitochondira make about 15% of then genetic material in a human cell. total chr1-22+X/Y ~= 6,200,000,000 (6.2 billion, sizeof genome = 3.1B times 2) sizeof one mitochondira : 16569 so ((100)(50016569))/6200000000 = .13362096774193548387
- Cogito 12y ago
  This calculation is looking at the amount of genetic material in a cell by (essentially) weight. Let's take that as the right way to compare these for a moment. ---- Nuclear genome (no sex chromosones): 2,881,033,286 base pairs Sex chromosones (avg): 262,592,623 base pairs (310,541,120 women, 214,644,126 men) Nuclear genome (avg): 3,143,625,909 base pairs Mitochondrion genome: 16,569 base pairs mtDNA in a cell: 500 ---- The proportion of genetic material in a cell that comes from mtDNA is thus: (total mtDNA) / ((nDNA no sex) * 2 + (nDNA sex) + (total mtDNA)) (16,569 * 500) / (2,881,033,286 * 2 + 262,592,623 + 16,569 * 500) which is 0.00137, or 0.137% If we look at just the amount of information encoded, we get: (mtDNA) / (nDNA + mtDNA) (16,569) / (3,143,625,909 + 16,569) which is 5.2710^-6 or 0.000527%

by Cogito 12y ago

Crito 12y ago

How do mitochondria replicate their own DNA? Do they somehow have the rest of the cell do it, or do they contain/produce and use all of the necessary enzymes/proteins/base-pairs/etc to do it by themselves? The relationship between them and their host cell almost seems similar to ant-fungus mutualism.

schoen 12y ago
This is actually a now-standard theory of the origin of mitochondria (that they were originally separate organisms): https://en.wikipedia.org/wiki/Symbiogenesis https://en.wikipedia.org/wiki/Symbiogenesis
jforman 12y ago
All of the DNA replication machinery that operates in mitochondria is encoded in the nucleus, translated in the cytoplasm, and then transported into the mitochondrion: "The remaining ~1500 mitochondrial proteins are encoded in the nucleus, including all proteins needed for replication and expression of the small mtDNA genome (Falkenberg et al., 2007)" from http://ac.els-cdn.com/S0092867409012458/1-s2.0-S0092867409012458-main.pdf?_tid=96f8c212-ac13-11e4-ac6b-00000aacb35e&acdnat=1423016266_587dd8a75f971860b976b3ea016b270f http://ac.els-cdn.com/S0092867409012458/1-s2.0-S009286740901...

gameshot911 12y ago

>Those who think this is the start of ever more invasive genetic modification of humans, or so called "designer babies" Well...this is the start of ever more invasive genetic modification of humans.

Cogito 12y ago
I guess it is! That said, I don't think the 'slippery slope' arguments made in parliament are valid, precisely because this is a very specific kind of genetic modification: > "But one thing is for sure, once this alteration has taken place, as someone has said, once the gene is out of the bottle, once these procedures that we're asked to authorise today go ahead, there will be no going back for society." Replacing mitochondria is very different to designing genetic traits, either through careful selection of eggs and embryos, or splicing, and I think that conflating the two is silly. If laws were introduced that would allow modification of the primary genetic material that debate would be had then. This law will not shoo-in laws that provide for that kind of genetic modification.
- 2muchcoffeeman 12y ago
  The 'slippery slope' argument also seems easy to fix in this case. Can't we just extend whatever laws with the addition of this specific treatment? Anything else has to be looked at on a case by case basis.
  - skore 12y ago
    > Can't we just extend whatever laws with the addition of this specific treatment? Anything else has to be looked at on a case by case basis. Cue people shouting about how politics are slow and killing people while also forcing politicians into making medical judgements that they may not be qualified for, further increasing the chance that they become the playthings of lobbyists who "do their homework for them". I'm utterly divided on this issue by the way, just noting the inevitable discussion that follows your logic.
- one-more-minute 12y ago

recibe 12y ago

Opposition is also from those who don't think that human reproduction is a moral imperative to be guaranteed by the state - under the fallacy that it somehow increases our collective quality of life. Like me.

one-more-minute 12y ago
That's an interesting point, and perhaps a good argument for not diverting public health resources towards this kind of procedure (I'm sure there are good arguments for the opposite, too). But there's a big difference between not actively endorsing a procedure like this and making it illegal.
- recibe 12y ago
  Not really. This procedure is likely to be inaccessible to the general public without subsidy via insurance (public or private). My argument is that one's ability to reproduce should not be guaranteed by the state, and therefore the state should not create laws that overtly or inadvertently sanction the genetic engineering of eggs or embryos to that end. This law does precisely that.
  - one-more-minute 12y ago
    > one's ability to reproduce should not be guaranteed by the state, and therefore the state should not create laws that overtly or inadvertently sanction ... Ok, but even taking the first part of that as given I don't understand why the second part follows. I don't think one's ability to go on holiday should be guaranteed by the state, either, but that doesn't mean plane travel should be illegal.
    - recibe 12y ago
      From the article: "The method, which was developed in Newcastle, should help women like Sharon Bernardi, from Sunderland, who lost all seven of her children to mitochondrial disease." Reasoning: Sharon Bernardi hasn't been able to reproduce naturally without this "method". But the UK is going to make this method legal - and because its healthcare system is publicly funded the UK government (and thus the public) will also pay for the implementation of the method. This represents an example where the state is making a guarantee - a formal promise or assurance - that it will pay for citizens that normally couldn't have children to be able to have them. From the article: Prime Minister David Cameron said: "We're not playing god here, we're just making sure that two parents who want a healthy baby can have one." What's not logical about that?

tosseraccount 12y ago

"This is around 0.1% of the total genetic code." More like 13% ... check my math ... Most chromosomes have 2 copies per cell. However ... there are many copies of the mitochondria : http://en.wikipedia.org/wiki/Human_mitochondrial_genetics#Quantity http://en.wikipedia.org/wiki/Human_mitochondrial_genetics#Qu... <i> Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500.</i> Mitochondira make about 15% of then genetic material in a human cell. total chr1-22+X/Y ~= 6,200,000,000 (6.2 billion, sizeof genome = 3.1B times 2) sizeof one mitochondira : 16569 so ((100)(50016569))/6200000000 = .13362096774193548387

Cogito 12y ago
This calculation is looking at the amount of genetic material in a cell by (essentially) weight. Let's take that as the right way to compare these for a moment. ---- Nuclear genome (no sex chromosones): 2,881,033,286 base pairs Sex chromosones (avg): 262,592,623 base pairs (310,541,120 women, 214,644,126 men) Nuclear genome (avg): 3,143,625,909 base pairs Mitochondrion genome: 16,569 base pairs mtDNA in a cell: 500 ---- The proportion of genetic material in a cell that comes from mtDNA is thus: (total mtDNA) / ((nDNA no sex) * 2 + (nDNA sex) + (total mtDNA)) (16,569 * 500) / (2,881,033,286 * 2 + 262,592,623 + 16,569 * 500) which is 0.00137, or 0.137% If we look at just the amount of information encoded, we get: (mtDNA) / (nDNA + mtDNA) (16,569) / (3,143,625,909 + 16,569) which is 5.2710^-6 or 0.000527%