Crispa + Cas9

[woolyhead 15]

Has anyone heard of the CRISPA method of targeted gene manipulation? Leaving aside the ethical discussions, there is something else that I would like to know. The human body contains some 30 trillion (3 x 10 exp13) cells and there are some 200 germ lines. So how much gRNA is needed to correct all the faulty DNA bases? 

[CarolW 10]

I've heard of it but know very little about it  - I think it's a method of snipping out faulty gene segments, and then replacing them with others... It's called "CRISPR" - this article should explain more... https://ghr.nlm.nih.gov/primer/genomicresearch/genomeediting

[woolyhead 15]

Thank you Carol. The article you gave does indeed explain what CRISPA is and roughly how it works but I am interested in finding out how many pieces of gRNA  it takes typically to correct a genetic fault. The reference doesn't tell us. The number of cells in a body is arguably around 30 trillion (3 x 10 exp 13) and, the cells altogether contain 200 germlines. So each genetic fault (one germline per fault) will contain either more of less than round about (3 x 10 exp 13)/ 200 identical pieces of faulty DNA. So if one dose of correcting gRNA is injected into someone it would have to contain an awful lot of correcting gRNA.  I'm trying to find out approximately (ball park) how much is necessary for correcting any given genetic fault, say for e.g. sickle cell anaemia. Does anyone on this forum know or could you please find out for me?

Edited March 10, 2020 by woolyhead

[geared 300]

I don't think it's been widely trailed on humans yet, so the answer may not be out there.

 

It's an extremely touchy subject, even though there are powerful medical uses for it. 

I think a Chinese scientist used it on a human embryo a while ago?  He was vilified in the media.

[woolyhead 15]

Yes, as you say, extremely touchy.  There are commercial businesses who say they can correct faulty human genes so I tried to get the answer from one of them but they didn't reply to my e mail. I think they wanted to first find out if I was genuine and then no doubt get hold of my bank details. Dominic Lawson of the daily Mail wrote a column on Feb 24th about the subject from the viewpoint of the strong anti-lobby.

Edited March 13, 2020 by woolyhead

[geared 300]

I saw on telly a report about the underground community of people who are experimenting it on themselves.

 

It was a worrying watch tbh.  They call themselves genehackers or something. 

[woolyhead 15]

That sounds dangerous! I know the actual correcting of DNA is guided by a synthetic RNA strand and implemented by a Cas 9 bacterium. Finding your own DNA is done quite a lot nowadays and because it only involves taking saliva and placing it in an analyser it seems like quite an  innocuous thing to do to yourself. But making the right synthetic RNA, called gRNA, seems to me to be very problematic. You would need to know which piece of the DNA you wanted to change and what to change it into.  Changing it sounds simple … you just inject Cas 9 and that does the job for you. But it can't really be that simple of course. And the next question is how many of these gRNA strands are needed? None of the videos I've seen on the whole subject so far tell us this degree of detail. Maybe this is just part of what these DIY experimenters are doing?

Edited March 17, 2020 by woolyhead

[Magilla 510]

On 09/03/2020 at 12:00, woolyhead said:

Has anyone heard of the CRISPA method of targeted gene manipulation?

I hadn't until recently, there was a BBC Storyville about it a few weeks ago which was fairly informative:

https://www.bbc.co.uk/iplayer/episode/m000dt7d/storyville-the-gene-revolution-changing-human-nature