Page 99 - The Secret Museum

Miescher found out about DNA – which he called nuclein – when, doing a grim-

sounding experiment on cell-digesting, he extracted some enzymes from a pig he had
bought at a butcher’s and some cells from bandages used by a soldier during the
Prussian War, which was going on at the time. He suggested that nuclein might be
involved in heredity, but then discounted his own idea, saying it wasn’t possible that
one single molecule could account for all the variation seen within species. He
thought that would be far too simple.

So Francis Crick and James Watson, helped by the work of Rosalind Franklin,
didn’t discover DNA, but they did work out what it looked like. They struggled to

conceptualize the exact shape of the molecule for years, and were helped enormously
by Rosalind Franklin’s skill as an x-ray crystallographer.

Franklin had spent four years researching crystals in Paris before moving back to
London to work on investigating the structure of DNA. She was given jam jars full of
gooey DNA and began to take x-ray photographs of it.

Meanwhile in Cambridge, Crick and Watson made a homemade metal model of
DNA as a way to represent, in reality, the ideas they were carrying around in their
heads. They had several false starts. They made a triple helix in 1951 and invited
Franklin to see it, and she pointed out the molecule as they had made it would never

hold together. In 1953, after seeing a photograph taken by Franklin, their ideas fell
into place. Finally, they got the model right, and made their physical double helix.
This sketch was made around the same time: it was part of the process of grappling
with exactly what the DNA molecule looks like. When finally the image became
crystal clear in their minds, the scientists were ecstatic. Crick said, ‘It is not easy to
convey, unless one has experienced it, the dramatic feeling of sudden enlightenment
that floods the mind when the right idea finally clinches into place.’

Crick and Watson published their realization in the 25 April 1953 edition of

Nature. The order of the names on the paper (Watson and Crick) was decided by the
flip of a coin. The pair went on to win the Nobel Prize for their discovery, along with
Dr Maurice Wilkins; Franklin, who had been pivotal to the research, died before the
prize was awarded. Hopefully she would also have been honoured with the prize,
had she been alive to receive it, for it would not have happened in the same way
without her.

Now we know that a DNA molecule looks like the image in the sketch: a double
helix. Every living creature on earth is made up of right-handed spiral shapes like

this. The sketch, according to experts at the Wellcome Collection shows a few key
features of the molecule. It is right-handed, it has two strands running in opposite
directions, and the building blocks of the strands (nucleotides) have one part that
forms the backbone of the molecule and another (the base) that sticks out into the
middle of the helix to join with a base on the opposite strand. This joining of two
bases is essential in order for DNA to pass on genetic information from one
generation to the next. That’s quite a lot of information, crucial to our existence on