There are three major streams of information that now come together. The first information or area of research was my discovery that human and animal cells have a finite capacity to divide or replicate in culture, and probably in vivo that is within the body itself, although I won't address that subject.

And the second area of research was the problem of what we called the 'three-prime overhang in DNA', which is the technical term, which means that as DNA replicates, as each round of cell division occurs, the mystery was that the DNA molecule would become shorter and shorter and shorter. And that implied that genes would be lost at each round of division if this happened, and so we knew genes weren't lost and there must be an explanation for that. It was Alexey Olovnikov, the Russian scientist, who, in an armchair, dreamt up an explanation for this phenomenon and I believe... and I described that earlier. That was also an effort to understand... that was also made by James Watson, the discoverer of DNA, the structure of DNA.

And a third area was what I just described, and that is the discovery by Calvin Harley and Carol Greider, who had this accidental meeting at McMaster University in Canada, to look at my cell system in respect to the behaviour of the telomeres, that is the structures at the ends of chromosomes that she was expert in. And lo and behold, she and Calvin Harley discovered that as the cells divide and get closer and closer to the point where they stop dividing, the telomeres, which are structures at the ends of the chromosomes so they're quite long, become shorter and shorter and shorter. And because they contain only nonsense information, they behave like a buffer, and consequently as they are lost at each round of division, it has no consequence in respect to the... any danger to the genes in the rest of the chromosomes. But what it does have an effect on is that as it... as these telomere structures are lost at each round of division and they get closer and closer to the DNA, the active and important DNA itself, they... it apparently triggers events downstream that tell the cell to stop dividing. It also tells the cell to do a lot of other things, but those are too detailed, but the major thing is that they tell the cell to stop dividing.