• Question: How does gene therapy work,considering how small dna is?

    Asked by chilechich to Adam, Joanna, Louise S, Louise W, Marcus on 14 Nov 2012.
    • Photo: Adam Paige

      Adam Paige answered on 14 Nov 2012:

      We have learnt how cells build DNA and how they cut it up into pieces and how they stick it back together again. We then used the same things that cells do, but we put all the parts in a tube to do it. So we cut, stick or make DNA using the same enzyme proteins that the cells use (which we purified from the cells in fact). This enabled us to build DNA how we wanted it. So we can put the healthy gene we want to put into a patient into a small circular piece of DNA called a plasmid, or into a virus DNA. The plasmid or virus helps the healthy gene get into a patients cells. Then the healthy gene should make its healthy protein and make the cells work properly.

      It is easy to make the DNA, what is difficult is getting it into the patients cells. Most of our cells (for example our liver or heart) are hidden away in our bodies and we cant get to them. Years ago I worked in a department that had the first UK licence to do gene therapy to help cystic fibrosis patients. They wanted to get their DNA into cells in the lung so they got patients to breathe in the healthy gene in a virus that is good at getting into lung cells. It didn’t work as well as they hoped and their has been lots of work since then to improve our technologies. But there are a few diseases now that gene therapy works really well for.

    • Photo: Joanna Giles

      Joanna Giles answered on 14 Nov 2012:

      Hi!
      Yes, as Adam said DNA can easily be manipulated these days because we know quite a lot about it.

      DNA is a small molecule, but only because it is folded up so much into our cells. Did you know if we unwound the DNA from a single cell it would be over 3 meters long! Just really thin, so you wouldn’t see it!

      Gene therapy though looks at only replacing one single gene at a time. So one gene that doesn’t work needs to “be replaced” in the cell of interest.

      Diseases like Cystic Fibrosis has just one single gene that doesn’t work and so scientists are trying to figure out ways of getting that one single gene into the cells. Once the gene is there, the cell will copy it and “translate” the message into the working protein using all the clever machinery that it already uses for all the other genes in the cell.

      However, lots of diseases are be caused by multiple “faulty” genes and so it will be more difficult to use gene therapy to try to treat those diseases.

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