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Rights: The University of Waikato
Published 16 November 2007 Referencing Hub media

DNA is an enormously intricate yet simple molecule. It organises living things. How does it work? Why do some say it is so beautiful? How should we think about it?


Sir Paul Nurse: What we have to do in explaining how living things function, is think about what living things are actually doing at the highest level. Because living things have characteristic phenomena; phenomena which are common to all life. They are sensate, that is they can sense what is going on around them. They are homeostatic, that is, they maintain themselves. They can communicate, within cells, between cells, between tissues, between organisms. Life reproduces, so it has inheritance, it adapts, it evolves. And it's self-organised, it organises itself in space and in time.

These are all high level functions, and to understand how life works we have to think how the physics and chemistry going on in life can generate that. And my suggestion is that we focus on the information that underpins these processes.

So let's talk again about DNA and the structure of DNA. Because what is beautiful about DNA is not the double helix; what is beautiful about DNA is what it means for inheritance. Let's unravel that helix. DNA is essentially like a ladder with rungs, and we have a series of letters down one side of the ladder and a series of complimentary letters down the other side of the ladder. And we have four letters, a G,C, A and a T, and it turns out that what happens is that the G on one side of the rung always forms a linkage with the C on the other rung, and an A will always form a linkage with a T.

And the order of those letters can be copied by taking that ladder, splitting it apart and then remaking another side of the ladder using those pairing or coding rules, of G matching with C, and A matching with T, and so every time you do that you will produce two exact copies of the ladder, and that happens every time that a cell divides, it produces two exact copies of the ladder. So you have a structure that can encode information and can replicate information. And that emerges from the chemistry and it emerges from the nature of the molecule, but it's not the chemistry that is interesting, it’s what that chemistry means for information within the cell that is interesting.