The Guardian view on adjusting DNA: a new world

["Dave Farber" <farber () gmail com>]

> Begin forwarded message:
>
> From: Dewayne Hendricks <dewayne () warpspeed com>
> Subject: [Dewayne-Net] The Guardian view on adjusting DNA: a new world
> Date: August 4, 2017 at 12:15:58 PM EDT
> To: Multiple recipients of Dewayne-Net <dewayne-net () warpspeed com>
> Reply-To: dewayne-net () warpspeed com
>
> The Guardian view on adjusting DNA: a new world
> A hope that embryos could be purged of a genetic disease has been fulfilled in part. However, we are some way off 
> reimplanting modified embryos into their mothers – for all the right reasons
> By Editorial Board
> Aug 3 2017
> <https://www.theguardian.com/commentisfree/2017/aug/03/the-guardian-view-on-adjusting-dna-a-new-world>
>
> The news that a team of scientists from America and Korea have corrected a genetic defect in single-cell embryos is 
> tremendous. In the short term it affirms the revolutionary principles of the gene editing technique known as Crispr – 
> or, formally, Crispr-Cas9 . In the medium term it holds out the prospect – if the law changes – of eliminating some 
> single-gene defects from entire families, since embryos treated in this way will no longer transmit the defective 
> form of the gene. In the long term, the prospects for widespread genetic manipulation of humans are chilling as well 
> as exhilarating.
>
> Crispr makes it possible to manipulate a genome in the way that we can alter the words in a word processor. Very 
> small identifying stretches of DNA around a defective gene can be targeted and then deliberately broken. The hope is 
> that when the cell repairs the break, it does so without the original error. When the DNA is copied at the next cell 
> division, only a functioning version of the gene is reproduced. When this is done early enough, at the embryo stage, 
> the change does not last only for the patient’s lifetime, but is transmitted to all their descendants, too.
>
> Changing words or genes successfully requires in both cases that we grasp their meanings, and here lies one of the 
> dangers that have made most scientists extremely cautious about applying the technique to humans. The process by 
> which genes are used to build the bodies around them is extremely complex and we understand what happens when it goes 
> wrong much better than when it goes right. Crispr, although it appears to be very precisely targeted, can make errors 
> analogous to a badly framed search-and-replace request, changing gene sequences that are far from the intended 
> targets.
>
> Previous attempts to extend this technique to human embryos, in China, are reported to have run into problems with 
> mosaicism, where some, but not all, the copies of the relevant gene are changed, so that the embryo develops with 
> different regions expressing different variants of the same gene. The effects can be appealing when applied to cats. 
> It is not desirable in other contexts. That is one of the technical problems that the latest experiments have 
> overcome. Another was that the right part of the genome was edited. In the latest paper researchers looked at an 
> inheritable heart disease caused by an error in a single gene which affects about 1 in 500 adults. Even when it is 
> not fatal, it causes great misery, since a diagnosis means that you could die at any moment, and may transmit this 
> condition to your children.
>
> [snip]
>
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