The Listener 11 July 1974
The Race for t e Double Helix-
providence and personalities
Dr Francis Crick and Professor James
Watson discuss their Nobel Prize achieve-
ment, in discovering the genetic function
of DNA. The commentary is by Professor
Sir Michael Swann, chairman of the
fC&xrnors of the BBC.
FRANCIS CRICK: Why does a calf look like
its mother, or, for that matter, why do
cows always produce calves and not rabbits?
The scientist w.ants to know the details of
the process of inheritance. We know that
one sperm from a bull is enough to ferti-
lise a cow and produce a new individual,
with four legs, a head, all the details
right, and diff'erent from any other cow.
All that infor,martion (or, at least, half of
it) has to be contained iln thie minute head
of this very tiny sperm. That shows that it
must be written in- a very minute lan-
guage, a chemical language. Not only that:
when the egg has been fertilised, it pro
duces millions of cells. In each one of those
cells there's a precise. copy of all that
genetic information. Wlhen I left physics
25 years ago it seemed to me that these
two problems, how genetic information is
stored in such a small space, and ho,w it is
copied exactly, were the most important
problems in biology.
MICHAEL SWANN: A young American, James
Watson from Harvard, and two English+
men, Francis Crick from Cambridge and
Maurice Wilkins from London, were
awarded ,the 1962 Nobel Prize for Medicine.
They discovered the nature of ,the inherit-
  ance   chemical-DNA-deoxyribonucleic
acid. But before the moment of elation,
there were blunders, frustration, conflicts.
  Cambridge in the early 1950s was the
setting for Watson and Crick's part in the
DNA story. After the war, this was a
rather exciting place: a lot of us, young
and not so young, had come back to do
bi'ological research. I myself was doing
cell biology. There was a lot of interest
in the chemistry of life, and foremost
amongst the characters arou'nd the place
were Francis Crick and Jim Watson.
Crick was already about 35 `and he hadn't
even finished his own doctora t'hesis,
though I remember he was remarkably
good at giving advice to other people on
solving their dloctoral theses. Watson was
a very bright young American who hadn't
done a great deal. Crick was a physicist:
be didn't know much about biology, and
Watson didn't know much about molecules.
  What is it in living cells that carries
the genetic information? What spe&es
how an organism grows? At one level,
chromosomes are the answer, and within
the chromosomes, the genes. But how does
a gene work and what is it made of? By
the end of the 1940s it was becoming
clear that DNA was the most likely can-
didate. Professor John Randall had set up
a group at King's College, London, to in-
vestigate the processes in living cells. A
member of Qhis group was Maurice Wilkins.
MAURICE WILKINS: I was a physicist who
had worked during the war on the atom
bomb. I was rather disgusted by the way
in whioh science was being misapplied,
and so I wanted to get out of physics.
There were bigger potentialities for using
science in a beneficial way in biology.
MICHAEL SWANN: Wilkins's work on genetic
material took him on a visit to Naples
early in 1951. W(hile there, he gave a talk
on DNA. In the audience was Jim Watson.
JAMES WATSON: I suddenly became aware
$h.at there existed somebody who was try-
ing- to solve the ,structure of DNA, which
seemed to be a likely candidate for the
gene. Maurice was deadly serious, and I
tried to talk to him., but he's English, he
doesn't talk much with strangers. It wasn't
an obvious coming together of like minds.
MICHAEL SWANN: Jim Watson realised that
England was the ,ideal place ,to pursue his
DNA interest. By a lucky accident, he
managed to obtain a place at Cambridge.
JAMES WATSON: My first couple of months
in Cambridge were terribly chaotic. I went
to a dismal place with a landlady who
wanted me to take off my shoes when I
came in at, night, and didn't want me to
flush the toilet after ten in the ev,ening.
None of these things bothered me because
I'd met Francis, and i,t was a tremendous
change. Before then, I ,had been with lots
of bright people, but I couldn't agree with
any of them. Our thoughts were somewhat
dominated by Linus Pauling, because he
was the great chemist who was going to
solve biology.
FRANCIS CRICK: Had you met Linus?
JAMES WATSON: He smiled at me. We were
in the washroom of the Athenaeum, the
faculty club. of Caltech, and Linus Ilooks
down at me and smiles. I think it's a
Linus Pauling: he caught a cold
41.
strange place for this to happen.
MICHAEL SWANN: Linus Pauling, then Pro-
fessor of Chemistry at the California Ins&
tute of Technology, is one of the most
eminent chemists of this century. He was
awarded the Nobel Prize for his work on
the chemical bond. He came to public
notice recently, through his suggestion that
vitamin C could fend off the common cold.
In the late 194Os, brilliant insight en,abled
Pauling to work out an element in the
structure of proteins-the alpha helix.
LINUS PAULING: 08ne day, when 1: was the
Eastman Professor at Oxford in the Spring
of 1948, I caught a cold-it was before the
vitamin C days-and, after a day or two
in bed, reading science fiction, I got tired
of that and I thought: why don't I discover
the alpha helix? I took a piece of paper and
I drew on it a representation of an exq
tended polypeptide chain with the dis+
tances approximately right and th,e angles
righlt, except for one. So I folded the paper
and, finally, I found a way, by folding the
paper, to make this bond angle have the
value 110 degrees. I finally foand a way
of folding, such that a hydrogen boned held
the helical structure together and had just
the right dimensions.
FRANCIS cnrcr~: Linus Pauling was a genius
at this sort of thing. He was capable of .    '
taking short cuts. What we decided was
that we'd try and use the same met:hod..
MICHAEL SWANN:  It was known that
there were hundreds of sub-units in the
DNA molecules, so that there were un-
doubtedly millions of possible combina+
tions, and one needed to know which was
the right one. One needed some hard ex-
perimental data on DNA, and the only
place where that was coming from at the
time was King's C8011ege, London.
RAYMOND GOSLING:  Professor Randall was
using an electron microscope to look for
t,he genetic structure in ram sperm. As a
junior research student at the time, I was
given the job of persuading a whole heap
of ram's sperm to lie down in a'n orderly
fashion and try to get a diffraction photo-,
graph of `them. Not getting a very clear
picture, I went *to Maurice Wilkins, who
was looking at extracted DNA, and he had
found Chat you could pull it into fibres. I
used these fibres to make a specimen to
give me a DNA pattern ,that I could com-
pare with the ram's sperm pattern. With
the. original camera., we had a fairly weak
X-ray beam. We wanted a much more
intense beam that would let us look at
single DNA fibres. An X-ray set had just
been developed that enabled us to get dif-
fraction photographs from a smaIl crystal*
line region within one single fibre.
MICHAEL SWANN: Deciding what these pie-'
tures said about DNA's structure needed
the special expertise which Rosalind Frank+
lin brought to the King's College group.
AARON KLUG: I first met Rosalind Franklin
in late 1953 at Birkbeck College, where we
both came to work on problems of virus
structure. I was, perhaps, her closest and
certainly her last scientific colleague until
her death four years later. Within a short
time of her arrival at King's, she got excel-
lent clear pictures which could be used for
quantitative analysis.
MICHAEL SWANN: Scientifically, the King's

Rosalind Franklin: prepared to discount Crick and Watson as serious competitors
College work was going well, but pemmal
relationships between Rosalind and Mau-
rice Wilkins had become rather strained.
FRANCIS CRICK: Rosalind Franklin was a
professional crystallographer and I think
she regarded Maurice as being less so.
JAMES WATSON: It was in the days before
Women's Lib-which, she felt, was long
overdu,e. Women were badly discrimin-
ated against, certainly in King's College. I
think Maurice, when he brought Rosalind
in, afterwards regretted he'd given away
his problem.
MAURICE WILKINS: I was a general physical
molecular biologist, and I hadn't spekial-
ised in X-ray diffraction methods. Rosalind
Franklin was brought into this work be-
cause she was experienced and a specialist.
If you regard getting the structure of DNA
as a race, we lost very early on, because we
didn't find it possible to work together.
RAYMOND GOSLING: Maurice was a reserved
person. Rosalind was intense, and so they
were about as different as you could get.
FRANCIS CRICK: But how did you get on
with Rosalind?
JAMES WATSON: `Terrible.
FRANCIS CRICK: She didn't think you knew
much crystallography.
JAMES WATSON: She was totally correct.
MAURICE WILKINS:  Rosalind was rather
prepared .o discount Crick and Watson as
being ver 5 serious competitors. There was
a general impression that they were like
butterflies; they were flitting around with
lots of brilliance but not much solidity.
Obviously, this was a ghastly misjudgment.
MICHAEL SWANN: When Rosalind Franklin's
pictures were good enough to analyse, she
presented her results at a meeting in 1951.
JAMES WATSON: It was in King's, next to
Somerset House. It was a very old place,
almost Dickens-like.  Not many people
really cared about what Rosalind said. It
was a small audience. I made a terrible
mistake-
FRANCIS CRICK: Being a new boy in crystal-
lography, how were you to know the differ-
ence between a unit cell and the asym-
metric unit?
JAMES 'WATSON: So I got water wrong, by
a factor of 24 or somethin,g.
FRANCIS CRICK: Wh'en Jim reported what
she said, it seemed that it was a dry
structure. Actually, the facts were that it
was extremely wet; this was due to the
misunderstanding of two technical terms.
So we had an abortive attempt trying to
solve the structure as if it were dry. We
even went so far as to build models.
JAMES WATSON: We called up the people
at King's and said we had solved it. They
came up, scared to death that we might
have, and probably also sceptical. Rosalind
didn't really think this was going to work.
When we started explaining things, she
immediately asked : ` Where is the wa.ter? '
I said: `There wasn't any. You said that.'
And, of course, she said: ' I didn't say
that.' I felt rather stupid.
MAURICE WILKINS: The Cambridge model
really was an embarrassment to us. To
see these highly intelligent' Cambridge
chaps turning up something crazily wrong.
The whole thing was inside-out.
JAMES WATSON: It had the effect of cry-
The Listener 11 July 1974
ing ` Wolf! `. Up to then, if we asked
them for some data, they would tell us.
MICHAEX SWANN: The fiasco over the model
irritated Sir Lawrence Bragg, who was the
head of the Cavendish Laboratory. Crick
didn't endear himself to Bragg. I remem-
ber Bragg once saying to me that Crick's
extrem'ely penetrating voice made his head
buzz. This last trouble wasn't the only one,
because, some months earlier, there'd been
a problem over scientific priority.
JAMES WATSON:  As far as I could tell,
Francis had told the Professor he'd stolen
his ideas. Bragg t,old me afterwards he
didn't want to go to the tea-room because
he'd have to hear Francis's voice. It would
remind him of this thing. From then on,
although Bragg had a lot of ambitions,
chiefly about proteins, one of his minor
ambitions was that Francis should leave
the lab.
MICHAEL SWANN:  Bragg wanted Crick to
stop talking so much and get on with his
PhD thesis, and so he actually ordered
Francis to stop working on DNA. Bragg
and Randall were two very powerful and
important figures. You might say they'd
really carved up the t,erritory between
themselves, because Bragg's lab at Cam-
bridge, it was agreed, would work on pro-
teins and Randall's lab in London, it was
agreed, would work on DNA. Protocol in
those days (and even today, as a matter
of fact) is really rather important. But, of
course, those sorts of restraint didn't apply
to Linus Pauling.
JAMES WATSON: In fact, Linus wrote me a
letter which said that he was going to
come to Europe and hoped he could talk
to me about our work on DNA. Pauling
really was interested in everything. We
kept telling Maurice this.
FRANCIS CRICK: Yes, we kept trying to
frighten him, like the mothers in the time
of Napoleon who used to try and send
their children to sleep by saying: `If you
don't go to sleep, Boney will come.' We
used to say to Maurice:  ` If you don't
solve the structure, Linus Pauling will
solve it.' But Maurice wanted to do it the
sound way, not be bullied by us.
JAMES WATSO~~: Maurice had told us that
Linus had asked him for the X-ray photo-
graphs. I think Maurice thought: `I don't
want to send Linus our data until we've
had enough time ourselves to look at it.'
LINUS PAULING: 1 wrote to Wilkins at King's
College, asking if I could have prints of
the photographs that he had olbtained,
but my effort was not successful. I con-
tinued to work on the basis of poorer
photographs, and this was in part respon-
sible for my failure to find the structure.
MICHAEL SWANN:  At the time Linus Paul-
inlg wanted to come to England, the MC-
Carthy purges were at their height in
America.  Because of Pauling's pacifist
sympathies, his passport was withdrawn
Some news of Linus's progress reached the
Cavendish through his son, Peter.
PETER PAULING:  My father wrote me a
letter saying that he had an idea for the
structure of DNA and was going to publish
`it in the Proceedings of the National
Academy of Sciences. He asked me whether
I wanted a manuscript copy of it.
JAMES WATSON: Of course, we were Upset.

The Listener 11 July 1974                                                                      43
The question was: could it be right? We
knew that Linus didn't have a good X-ray
photograph. So could he have thought it
through without any of the King's data?
PETER PAULING: In those days, I had no idea
what a gene was, no idea what DNA was.
This paper came, and I didn't know what
any of it meant. I gave it to Jim Watson
and Francis Crick. According to Jim, not
only did I noit know what nucleic acids
were, but my father didn't know either.
JAMES WATSON: He had decided that DNA,
which is deoxyribonucleic acid, wasn't, in
fact, an acid. I rushed around Cambridge
showing it to people, asking could it be
right? And they all said, no, it's an acid.
As the afternoon wore on, we had a feeling
of great relief: we still had a chance, the
problem hadn't been solved by Linus.
FRANCIS CRICK: More than great relief, Jim.
We were hilarious, I'm sorry to say. Linus
had bad luck. He had poor X-ray pictures
but, even worse than that, they were
misleading. They were really two X-ray
pictures on top of one anoither. It isn't
surprising he got it wrong. Now at King's,
they had much better X-ray pictures. An
X-ray picture is not a simple picture like a
photograph: to understand what you expect
from a helix, you have to work out a mathe-
matical theory which shows you what the
diffraction pattern would be. When Jim
went to King's with the erroneous struc-
ture of Linus Pauling in his pocket, he was
familiar with the X-ray diffraction theory.
JAMES WATSON: Maurice read it and, in his
usual way, didn't convey much enthusiasm
one way or the other, but I guess he said
he didn't think Linus was trying to get the
right structure. At the same time, however,
he let loose the bombshell, at least to me,
that actually there were two types of DNA
X-ray photographs: there was the form
which I knew about, called the A form,
which gave the crystalline pattern, but also
a second form called the B form. He
opened a drawer and took out a photo-
graph and, boy! I could hardly believe it.
hours a day. It's awfully hard to give up an
idea of your own, so I started putting the
phosphates in the centre-maybe because it
was like a Pauling structure. Francis wasn't
comfortable on this and asked me why not
try putting the phosphates on the outside.
AARON KLUG: Francis may have been play-
ing the devil's advocate in telling Jim to
try thle phosphates on the outside, but,
indeed, there were very good reasons for
doing so. Rosalind had said so at her col-
loquium in 1951, which Watson attended,
but he had not understood.
It was a perfect helix. So I said: `Maurice,
you got to build models.' But the trouble
was Miss Franklin. So I thought I should
go over and see Rosalind. I went in and
told her I had a copy of the Pauling
manuscript, if she would like to see it. It
was clear that she was annoyed at my
trying to tell her something about crystall-
ography. She came toward me. I thought
she was going to hit me. So I quickly got
out, at which point Maurice was coming
around, and she almost hit Maurice.
MAURICE WILKINS: Who hit who? I don't
JAMES WATSON: I cut some things out of
cardboard and made the right shapes and
pasted things on to indicate hydrogen
atoms. The following morning, I started to
put them together in pairs.
FRANCIS CRICK: In those days there was a
brilliant young theoretical chemist in
Cambridge, called John GrifIlths. He died
quit,e recently. One evening, we were
sitting in a pub and talking about biological
replication, and I sai'd to him: perhaps the
secret is that the bases attract each other
in pairs, but like with like-adenine going
with adenine, and guanine going with
guanine? I met him, later, in the tea-queue
at the Cavendish, and he told me he'd done
a few scribbles on the back of an envelope
and he'd found that it was not `like with
like `, but that adenine stacked nicely on
top of thymine, and guanine on top of
cytosine. He'd been thinking along those
lines at the time, but I didn't know that.
The relative of the four bases in DNA
had been worked out by a nucleic acid
chemist called Erwin Chargaff, a few years
before this time. It happened he was pass-
ing through Cambridlge and he tsold us
about his results, which were that the
amount of adenine equalled the amount of
thymine and the amount of guanine
equalled the amount of cytosine in all sorts
of DNA, wherever he looked, although the
other ratios were all over the place. Any-
body who knows about the history of
science knows that when you have one-to-
one ratios it means that things go together.
MICHAEL SWANN: The second clue came
when Watson started playing with card-
board modells of bhe bases. Watson sud-
denly saw that when A went with T, it
formed the same shape pair as when C
went together with G.
FRANCIS CRICK: Something came out of the
model-building which Jim had done which
he hadn't put in, and that's always the sign
that you're on the, right lines. Everything
was finished except the hard work of pro-
ducing an accurate model. Jim wasn't much
good at that sort of thing, the models
tended to flop about in his hands. I worked
oonltinuously for about four days, and then
came t.he point where we saw that every-
thing fitted, and I was so tired I went
straight home to bed.
AARON KLUG: In Jim's mind, Pauling was the
great rival but, in his rather perfunctory
contacts with Rosalind, he hadn't got the
measure of her at all. Indeed, he didn't
know that she was only one or two steps
away from the solution. But she didn't have
a collaborator with whom she could discuss
problems very closely, and she was one
person against this powerful combination
of two extraordinary people.
JAMES WATSON: Francis, do you think we
were lucky, or was it real brain work?
FRANCIS CRICK: I guess we were certainly
lucky, for two reasons. We were thinking
about the problem at the right time, and
then the two of us were collaborating:
when one of us got on the wrong track,
the other one got out of it. We weren't
the least afraid of being very candid
to each other, to the point of being rude,
and if you don't have constant inter4
change, saying what you think of other
people's ideas to their face, I don't think
you can solve problems of this kind.
JAMES WATSON: If either Iof us `had been
two years older or two years younger, we
would never have solved it. We had to be
there just at that particular time.
FRANCIS CRICK: We pooled the way we
looked at things. We didn't leave it that
Jim did the biology and I did the physics,
We both did it together, and switched roles
and criticised each other, and this gave us
a great advantage over the other people
who were trying to solve it.
From ` Horizon ' (BBC 2). Produced by
David Paterson.
think anybody hit anybody. Actually, some
people may have thought someone was
going to hit someone. There, certainly
weren't very friendly feelings.
MICHAEL SWANN: By now, Lawrence Bragg
had heard of Linus Pauling's attempts. NOW
Bragg wanted DNA to be a British success,
so he agreed that Jim Watson could start
working on DNA again. To represent the
structure, it was necessary to build models.
FRANCIS CRICK: We used balls to represent
atoms and rods to represent the bonds
between atoms. There is a very large
number of ways,. given the chemical
formula, that you can build the model.
JAMES WATSON: I would do it, maybe, three
Nobel Prize winners: Francis Crick, James Watson, Maurice Wilkins