Page last updated at 12:22 GMT, Thursday, 20 August 2009 13:22 UK

On the shoulders of biology's giants

By Dr Adam Rutherford
Presenter, Cell, BBC Four

DNA helix (SPL)
The story of DNA is a complex one

Physicists have long searched for "grand unifying theories" - the rules behind everything in the Universe.

So far, they have not succeeded. But in biology, it has happened three times.

A theory is a definitive model of reality, which not only describes the facts, but predicts the outcomes of experiments yet to come.

One of the first was "cell theory". In the late 17th Century a Dutch draper, Antonie van Leeuwenhoek, first saw living cells with a lens designed for looking at cloth.

In the 150 years that followed, cell theory emerged to irrefutably describe not only that every living thing on Earth was made of cells, but that cells could only be born from existing cells dividing.

Charles Darwin came up with the genius of the theory of evolution by natural selection in 1859: how life on Earth spread and evolved. The third was the discovery of the double helix of DNA.

This discovery revealed that there was one molecule, common to all life forms, which gave the mechanism for both cell theory and evolution.

Francis Crick and Jim Watson worked out the exquisite double helix in 1953. But science is an inherently collaborative game. Scientists build on the work of their predecessors and colleagues.

Scientific explosion

In the phrase made famous by Isaac Newton, one can see a little further "standing on the shoulders of giants". In the BBC Four series Cell, we tell the disparate stories of these giants.

The story of DNA is complex because of the explosion in scientific endeavour at the beginning of the 20th Century.

Friedrich Miescher
Friedrich Miescher was the first person to isolate the "stuff of life"

Dozens of strands of research were unwittingly leading towards Crick and Watson's breakthrough.

Evolutionary biologists were working out the patterns of inheritance in populations.

Geneticists were beginning to understand the concept of genes: how individual traits are passed from generation to generation.

Chemists were busy trying to work out the way biological molecules were built. And doctors were experimenting with bacteria and viruses to understand and cure diseases. All of these roads led to DNA.

But it all started with a largely forgotten 19th Century Swiss chemist called Johann Friedrich Miescher, the first person to isolate the stuff of life.

I've extracted DNA a thousand times using hi-tech equipment in a nice clean lab.

It's easy if you know what you're looking for. Miescher did not. He knew that he needed something that would digest cells, and he knew he needed lots of cells.

Blood and guts

The digesting enzyme he got from a pig's stomach, via a local butcher. And the cells? The Prussian War was raging at the time, so he collected the soldiers' blood-and-pus-soaked bandages, and squeezed out their white blood cells.

Another figure who contributed to the study of DNA was Rosalind Franklin. Using techniques that emerged from the Manhattan Project, Franklin was expert at creating X-ray images that revealed the structure of molecules.

James Watson and Francis Crick (SPL)
Watson and Crick earned the Nobel Prize for their discovery

It was her painstaking and brilliant work - given to Crick and Watson without her knowledge - that provided them with the realisation that DNA was the iconic two intertwined spirals.

Each thread carries the same but mirrored information, meaning that by splitting it in two, the code of life could be retained by both halves to form two new molecules. That is what allows cells - and life - to reproduce.

Often, the credit goes to the people who jumped the final hurdle. Crick and Watson, both brilliant scientists, went on to receive their well-deserved Nobel prizes and eternal fame in 1962. Franklin succumbed to ovarian cancer in 1958.

Nobel prizes are regarded by the public as the ultimate scientific gong. But they can only credit a handful of the people who saw furthest on the giant's shoulders. Should Franklin have got one? The question is academic because they are not awarded posthumously.

Her contribution to the discovery of the double helix was pivotal, but, ultimately, it was Crick and Watson's discovery.

The praises of Rosalind Franklin, along with the many other forgotten giants, should be sung for contributing to the understanding of life on Earth and the biological theories of everything.

The next episode of Cell will be broadcast on Wednesday, 26 August, 2009 at 2100 BST on BBC Four. Or catch-up on iPlayer

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