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Jimmy Doherty meets Steve Jones: Decoding DNA

Updated Tuesday 24th February 2009

Steve Jones explains the work being done to decode DNA

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Jimmy Doherty: How does this little blob of DNA have any relevance to all this work here?

Steve Jones: Well what all this amazing document here tells us is the actual detailed structure of that blob. Now, in the old days we’d cut up animals and plants with a scalpel or a pair of scissors but what’s been done here is a pair of molecular scissors with fantastic detail, fantastic sophistication, which have will actually cut your DNA and any other creature’s DNA into each of its thousands of millions of units. And this is just a tiny proportion of the total, part of your X chromosome. Now, to make a magnificent specimen of humanity like yourself you’d need, I think the figure is 2,246 sheets this size, 3,000 million DNA letters in your alphabet, and that’s pretty impressive, particularly when you look more closely and you see there’s actually only four of those letters in the language of the genes, A, G, C and T, and the way in which they’re ordered says an awful lot about you, your birth, your life, your death and, indeed, who you’re related to.

Jimmy Doherty: So this is a human being decoded?

Steve Jones: It’s a kind of funny human being, this one. This is a Mr Average Human Being, somebody who was put together from little bits of DNA from all across the world. But we’re past that now, we could do your DNA probably in two or three weeks, in a couple of years we can probably do it in a day and for $1,000.

Jimmy Doherty: You could decode me in a day.

Steve Jones: Well I couldn’t but these people here probably could.

Jimmy Doherty: Also, we’re not only just decoding the human genome but other species as well, to find out how we’re related to them.

Steve Jones: The great power of this molecule, which would have delighted Darwin, is that it’s the universal answer. This is a molecule which is found almost throughout the living world, from you and chimps of course, you and pigs, you and your pigs.

Jimmy Doherty: Yeah.

Steve Jones: You and your wheat, but also bacteria, parasites of different kinds, almost everything, and they’ve all got the same code which suggests actually that life only started once. You’re a living fossil, I’m a living fossil, you contain your entire evolutionary history in your genes, it’s laid out here, and by looking at this blueprint compared to the blueprint of a pig or a wheat plant we can find out just how you’re related, and if we assume that it changes at a regular rate, which it probably does, we can find out when you split apart. That really would have cheered up Charles Darwin.

Jimmy Doherty: And how closely related are we with something like a chimpanzee?

Steve Jones: Well, on the crude measure we share something like 98.8% of this sequence with a chimpanzee. It’s actually not quite as simple as that because a lot of this sequence doesn’t actually code for anything as far as we know. We’re a bit more different and we ask more sophisticated questions about the working proteins, but the evidence is pretty impressive that we’re very close. There’s a great line which came out shortly after The Origin of Species, Gilbert and Sullivan, you know, the people who wrote the Mikado, Darwinian man though well behaved is really but a monkey shaved. And you as a shaved monkey, that’s it.

Jimmy Doherty: That’s it. But it’s interesting because I mean in Darwin’s time you could make the leap of understanding from a chimpanzee to a human being because they looked very similar, but I mean to make the leap from say a mushroom or a plant to then human beings is much harder.

Steve Jones: Yes, I think Darwin never dared to make that leap. I mean I think he inferred that leap was there in some vague fashion, but now we can measure it. And we can measure it by looking in the same way as we compare you with chimps, just asking about the DNA changes, and the results are kind of surprising. We and chimps are cousins but us and mushrooms are second cousins, and so we’re, you know, what DNA does is knock us off this giant pinnacle of being special, we’re just kind of rather upper class mushrooms really.

 

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