• Question: Can DNA in humans be switched on that we wouldnt normally have? for example the GFP gene that you spoke of in the lecture? or babies in the woumb with defective genes; could their DNA be corrected by switching on genes that havent naturally developed?

    Asked by holz1 to Vicky, Stefan, Samantha, Rachael, Matt, Leila, Kara, Hayley, Haihan, Alison on 4 Jan 2014.
    • Photo: Hayley Lees

      Hayley Lees answered on 4 Jan 2014:


      Very good question!

      The simple answer is yes and no!
      Yes, in theory, because if a gene has simply not been switched on then all we need to do is switch it on, right? This is sort of easy (and by sort of, I mean it is difficult, but scientists have found ways to do this). The thing is, just switching a gene on isn’t necessarily a good thing – it wouldn’t mean that it is definitely doing the right job. Some genes are not simply just switched on and kept on, but are switched on and off and different times. We’d need to know when and where they are switched on, and for how long, if the gene was to act like it normally does. And that bit is quite tricky! Another thing that would make it difficult in reality is that it may be relatively easy to switch a gene on in one cell, but getting it switched on in all of the right cells is much more diffiuclt. If we can take a fertlized egg, and switch the gene on there, then all the cells that it divides into would have the gene switched on too (but again, that’s an oversimplification, but lets say that’s the case for now). If you wanted to switch the gene on past that stage – in a bay, a child, and adult, what ever – then on the whole you would find it very difficult indeed.

      Your idea of switching on defective genes in the womb is a fantastic one and that’s actually something scientists are trying to do. But for the reasons i’ve mentioned, it’s difficult. Another problem is that for some defective genes, it’s not just a matter of switching them back on. Some are defective, not because the ‘on/off’ switch is broken, but because there is something wrong in the coding sequence that makes the protein which they code for (we say the gene has a mutation). This is much more difficult to fix then a gene which is just switched off. For example, in a gene that is just switched off, sometimes we can add molecules to switch it back on again. But for genes which have a mutation, it’s the DNA which needs to be changed.

      Maybe you could be the first person to come up with a way to switch on faulty genes!

    • Photo: Stefan Piatek

      Stefan Piatek answered on 4 Jan 2014:


      Ah a lovely question, so I think that you’re asking if you can insert a new gene or replace a faulty one, is that right?

      Hayley already answered the question. We can make animals (mostly worms, mice and, flies) that have these genes inserted, but we have to take them from a single embryo to make sure this gene is in every cell of the body (we can alter the DNA of the embro cells and this means that all the cells made later have the same DNA).

      Doing this afterwards is pretty tricky, lots of our DNA is from viruses that can insert themselves into our genomes, actually making their DNA part of ours. In theory we could use these to insert genes, but it’s pretty tricky and there are lots of things that need to be worked out: safety, targeting the right cells, stopping the viruses from being infective, and a lot of other things that I haven’t thought of.

      The other added problem is that you could have the right code inserted but it still needs to be “turned on” at the right time and in the right places, which is a wonderful level of complexity

    • Photo: Haihan Tan

      Haihan Tan answered on 6 Jan 2014:


      Forcibly switching on a gene that is defectively off in cells is probably fairly easy with the molecular biology tools we have, but to reiterate what Hayley and Stefan have said, the real issue is to control the timings and exact places where the gene should be on in the animal. We are far from understanding the full complexity of regulation of genes, although we’re making progress! As for your example of the GFP gene, GFP is a gene that is not originally present in the human genome, and introducing such genes into humans would lead to all sorts of ethical problems. So I’d say that most efforts in modifying gene expression are centred around genes that we already have.

    • Photo: Leila Abbas

      Leila Abbas answered on 6 Jan 2014:


      I’m not so sure that we’ll get it to work in humans, but there’s been loads of research using embryos from the zebrafish (check them out here – their development is broadly similar to human or mouse embryos, with the added bonus that they’re transparent so you can watch cells moving about! http://www.youtube.com/watch?v=ahJjLzyioWM)
      Scientists have shown that in the zebrafish, it’s relatively simple to add back a normal copy of a mutant gene, and ‘rescue’ the genetic defect. We’re a long way off being able to do this in people, but you’ve got to start somewhere!

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