The Double Helix
c Pearson Education Limited 2008
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About the author
James Watson was born in 1928 in Chicago in the United
States. He studied first at the University of Chicago and
then took his PhD at the University of Indiana, winning
his doctorate when he was still only twenty-two. The story
of his career from 1950 to 1953 and the discovery of the
double helix are told in this book.
After receiving the Nobel Prize in 1962, Watson
moved from Cambridge to Cal Tech in California
where he worked until 1968. The second volume of his
autobiography, Genes, Girls and Gamow, was published
in 2001 and talks in detail about these years. It also deals
with his bumpy love life, ending with his marriage to his
present wife, Liz.
Summary
James Watson’s account of how he and fellow scientist
Francis Crick discovered the structure of DNA is a
famous piece of popular science writing. There is as much
about the personalities of the scientists involved in the
momentous race that finally identified the double helix as
there is about proteins and crystallography. Non-scientists
can enjoy his story of human achievement and weakness as
much as readers with a science background.
The events of the story take place over only three years,
from 1950 to 1953. It begins in the cold north of
Copenhagen, with Watson’s arrival in Europe in search of
a career. Various branches of science failed to interest him
and he is quite honest about his unfocused early working
life. Knowing that his real interest lay in understanding
genes, he moved to Cambridge University in England,
where he immediately teamed up with the excitable
Francis Crick. Crick’s loud voice gave many of his
colleagues a continuous headache.
Advances in understanding DNA were being made across
the Atlantic by a brilliant American scientist, Linus
Pauling. Watson and Crick know that time is short and
that they are in a race with Pauling to find the structure
of DNA. The middle section of the book deals with their
attempt to understand DNA by using models. They
can’t persuade any other scientists that theirs is the right
way, however, and after a failed first attempt, their work
on DNA stops. Having upset all the people who could
have helped them, it seems that Crick and Watson will
never make it. Life at Cambridge continues and Watson
has plenty to say about accommodation and meals in
Cambridge colleges.
In the final part of the book, the race to unravel DNA gets
hotter. Linus Pauling at Cal Tech in Pasadena, California,
is nearly there. He publishes a paper, but too soon.
Watson and Crick immediately realize that he has made a
fundamental error. Their desire to win the race sends them
running back to their DNA ideas and models. Watson
recounts how they arrive at the answer, finally winning the
support of their colleagues as they get there.
The story ends with Watson, aged only twenty-five, and
Crick, announcing to the world that they have uncovered
the nature of life.
Chapters 1–2: Watson introduced the main characters
in the story. These include Francis Crick, who will later
becomes his colleague, Max Perutz, who runs the unit
where Crick works, and Sir Lawrence Bragg the director
of the Cavendish Laboratory. Maurice Wilkins works
in London with his assistant Rosalind Franklin. Linus
Pauling is working on the structure of DNA at Cal Tec
in California. Watson explains that as a student he didn’t
study areas of science that did not interest him. Now he
needed this knowledge to do his research with DNA. He
worked in Copenhagen with biochemist Herman Kalckar,
who sent him to an animal study centre in Naples, Italy.
There he attended a meeting and saw for the first time, an
X-ray diffraction picture of DNA by Maurice Wilkins. He
tried, but failed to make friends with Wilkins. Whilst on
a trip to Geneva, he learns that Linus Pauling has shown
a model of the alpha helix, which he thinks is part of the
structure of DNA.
Chapters 3–4: Rosy Franklin wanted Maurice to stop
taking X-ray photos of DNA. Rosy was refusing to share
her results with Maurice until she gave a talk three weeks
later. Bragg threatened not to give Crick a research place
at the Cavendish after he completed his PhD. Max Perutz
James D. Watson
The Double Helix
c Pearson Education Limited 2008
The Double Helix - Teacher’s notes 2 of 5
Teacher’s notes
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and John Kendrew defended Crick. Bragg accepted that
he and Crick had had the same ideas independently but
he still did not like Crick personally and hated his endless
chatter.
Crystallographer V Vand suggested a theory for the
diffraction of X-rays by helical structures. Crick quickly
saw Vand’s theory was not valid but tried to find a more
accurate theory. He talked to Bill Cochran the cleverest of
the younger Cambridge X-ray people. The next day, Crick
told John and Max about his ideas. Bill Cochran also
thought Crick was right, but found a shorter, more elegant
mathematical system. They checked their ideas by looking
again at X-ray diagrams. The agreement was so good that
both the Linus model and the Cochran-Crick theory had
to be correct. They wrote a paper and sent it to Nature
with a copy to Linus Pauling for his comments.
Chapters 5–6: Rosy gave a talk on her results but
delivered it poorly. She thought X-rays were the only way
to find structure of DNA and playing with models was
a waste of time. Watson travelled to Oxford with Francis
Crick who asked about Rosy’s talk. Watson had not taken
notes and could not say how much water was in the DNA.
Crick showed that only a small number of structures
were possible with Rosy’s pictures and Cochran/Crick
mathematics. Crick thought one week of playing with
models would bring the answer.
At the same time there was competition between different
teams in the United Kingdom and the United States. In
the UK, there was also competition between teams in
Cambridge, Oxford and London.
Watson and Crick knew they needed different models.
A three-chain helix seemed good and fitted with Rosy’s
talk. Crick phoned Maurice Wilkins to check with him.
They planned to give a presentation to Maurice. Firstly,
Crick would present helical theory, then Watson and
Crick would explain how they developed their model.
On the day of the presentation Maurice said helical theory
was not new. Rosy was impatient and said there was no
evidence that DNA was helical. She became aggressive
when they presented a three-chain model. Watson had not
remembered the amount of water correctly.
After this Bragg told Watson and Crick to stop work
on DNA. Model work could be done at King’s London.
Crick said the Alpha Helix was part of a larger helix.
The ban on working on DNA did not stop them from
thinking about it.
Chapters 7–8: Watson received a letter from Washington
saying he was sacked but also offering money to work on
TMV. Watson read about earlier research on TMV by
Bernal, Fankucken and Schramm. He showed an X-ray
picture of TMV to Crick who saw helical structures. Hugh
Huxley taught Watson how to use the X-ray camera. They
heard news that Pauling was coming to London but the
US State Department had revoked his passport because
of his political opinions. Salvador Luria also could not get
a passport so Watson had to describe the American work
to a meeting in Oxford. Al Hershey had said that the key
feature of viral infection of bacteria was injection of viral
DNA – a powerful new proof that DNA is the primary
genetic material.
Rosy was saying her DNA was not a helix. Watson used a
new powerful X-ray tube to take photos of TMX. He took
a picture that showed a helical structure. He showed it to
Crick who saw the helix immediately. It was now clear no
more benefits would come from studying TMV.
Austrian chemist Erwin Chargaff at Columbia University
had studied DNA, in particular their purine A and G
bases and their pyramidine C and T bases. Chargaff could
not explain why some life forms had more A and T while
others had more C and G but thought it was significant.
Francis and chemist John Griffith discussed different
systems of gene copying. Some thought genes split in two,
others thoughts they joined like pieces of a jigsaw puzzle.
Chargaff came to Cambridge but he was not impressed by
Crick and Watson.
Chapters 9–10: Watson met Max Delbruck from Cal
Tech. Watson showed a TMV picture to Delbruck but it
did not convince him. Linus Pauling arrived. His talk only
restates his published ideas. Two weeks later, Watson met
Pauling in Royaumont. They talked about Watson doing
X-ray work with viruses in Pasadena. Linus Pauling’s wife
Ava Helen said her son Peter was coming to Cambridge
next year to work with John Kendrew. She asked Watson
to help him settle in Cambridge.
Watson started to be interested in sex between bacteria.
Cavalli-Sforza and Bill Hayes had discovered that bacteria
were male or female. Joshua Lederberg had proved they
showed genetic recombination. Lederberg thought each
contributed equal amounts of genetic material, but Bill
Hayes believed the amounts were not equal. Watson
read Lederberg’s papers. Francis Crick and Maurice
talked about Rosy’s lack of cooperation. Crick forgot
to tell Maurice about the agreement between Griffith’s
calculations and Chargaff’s data.
The Double Helix
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The Double Helix - Teacher’s notes
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Peter Pauling arrived in Cambridge saying his dad is
interested in coiling of alpha helices in hair protein. Crick
worked on coiled coils, with the help of Kriesel, they
found the correct figures and wrote a paper for Nature
before Pauling. Francis Crick planned to go to Brooklyn
for a year. There were more problems between Rosy
Franklin and Maurice. Watson was now at Clare College
but hated the boring English food. He had stomach pains
and went to the doctor but got little help. Odile and
Crick helped him to find better place to live and eat. Peter
Pauling got a letter from his dad saying he had a structure
for DNA.
Chapters 11–12: Two copies of Pauling’s paper arrived,
one for Bragg, and one for Peter Pauling. Watson and
Crick studied Peter’s copy. Pauling described a three-chain
helix with a sugar phosphate backbone at centre. Watson
saw it was wrong but did not know why. Pauling’s nucleic
acid was not an acid at all. Watson told Roy Markham
who confirmed that the chemistry was crazy. Crick and
Watson knew they had about six weeks to find the answer.
Rosy rejected Pauling’s idea because it was a helix. There
was almost a fight between Watson and Rosy. Maurice said
they had found new form of DNA called the ‘B’ structure.
Watson saw the pattern was unbelievably simpler. An
X-ray showed a helix clearly. R D B Fraser had tried to
make three-chain model for the structure without success.
Watson tried to find a two-chain structure.
Watson described the B form to Bragg and Max Perutz.
He wanted the Cavendish to make models. Bragg
encouraged him. Watson worked on a two-chain model
with the backbone at the centre, then a model with the
backbone outside.
Watson tried to study the chemistry of bases. Were there
two chains with bases held together by hydrogen bonds
between the same types of bases? The essential trick of
gene copying could come from the requirement that each
base in a newly produced chain always bonded through
hydrogen to a similar base.
Chapters 13–15: American crystallographer Jerry
Donohue said Watson had chosen the wrong physical
forms of G and T bases. Francis Crick also saw problems.
Watson realized that A bonds to T and G bonds to C.
This type of double helix suggested a much better form of
copying. They needed to make a model to check if these
ideas were correct.
But before they had checked, Francis rushed into the pub
saying they had found the secret of life.
Gradually they improved the model and showed it to
more colleagues. They discussed how to release the news.
Watson thought about how to phrase the letters he would
need to write. Bragg saw the model in the afternoon.
Bragg could see the logic of the model but was worried
about not checking with Alexander Todd. Maurice saw the
model and immediately liked it. He said he would return
to London to check the model with his X-ray pictures.
Two days later he phoned to say that he and Rosy found
the X-ray data matched the model. They were writing up
their results and wanted to publish at the same time as
Watson and Crick. Todd came to look at the model, he
congratulated them on their work.
Pauling heard about the double helix from Delbruck.
Pauling was excited but wanted to see the X-ray evidence
from King’s College. Watson and Crick started to draft
their paper for Nature. Crick added a sentence saying
that the pairing they had described suggested a possible
copying system for genetic material. Bragg saw the paper
and said he would send to Nature. Linus Pauling came to
Cambridge to see his son Peter and also to see the model.
He said Watson and Crick had found the answer. Watson
went to Paris with his sister and Peter Pauling to celebrate
Watson’s twenty-fifth birthday.
Background and themes
The illustration on the front cover is of a double helix
– the structure of a DNA molecule. A helix is a spiral.
A double helix consists of two parallel spirals.
Nature of scientific discovery: One of the major themes
of The Double Helix is the nature of scientific discovery.
Scientists start with complex evidence and they search for
simple explanations. Watson and Crick were searching for
a simple explanation for very complex evidence.
Scientific specialization: Scientists often specialize in
a small area of study. In The Double Helix, Crick and
Watson’s search for a simple explanation of DNA is made
more difficult by the poor communication between these
specialist groups.
Women in science: Watson paints a very negative picture
of fellow scientist, Rosalind Franklin, a woman alone in
a man’s world. In their Nobel lectures, Crick and Watson
did not even acknowledge her contribution to their
success. In the years before her death, both Watson and
Crick got to know Rosalind Franklin better, and saw her
as the hard-working and successful scientist that she was.
The Double Helix
c Pearson Education Limited 2008
The Double Helix - Teacher’s notes
of 5
Teacher’s notes
LEVEL 6
PENGUIN READERS
Teacher Support Programme
Discussion activities
Introduction
Before reading
1 Group work: Find out how much students know
about DNA and the discovery of its structure.
Encourage students to share their knowledge in
groups. Finally collect feedback from groups as a
whole class activity.
Chapters 1–2, pages 1–16
Before reading
2 Discuss: Talk about what Britain was like in 1950.
Remember it was a few years after the end of the
Second World War. What did towns look like? What
did people wear? What did they eat? What did they
do for entertainment?
After reading
3 Role play and group work: Make seven cards with
the names James Watson, Francis Crick, Max Perutz,
Sir Lawrence Bragg, Maurice Wilkins, Rosalind
Franklin and Linus Pauling. Have students choose a
card from the pack and introduce themselves to the
group saying what they do, where they work and who
they work with. Students must try to answer any
questions from the group. Tell students to use the
information from the Introduction and Chapters 1–2.
4 Research and group work: Working in groups
prepare a two-minute presentation on the Alpha Helix
using the information in the book and from research
from other books or the Internet. Let each group
present to the whole class and choose the best
presentation. Discuss why it was the best.
Chapters 3–4, pages 16–30
After reading
5 Role play: Have students work in pairs.
Student A: You are James Watson, a young American
man of twenty-three. You are going to meet Sir
Lawrence Bragg one of the greatest scientists in
Britain. Greet Sir Lawrence politely and introduce
yourself. Answer any questions he asks you about your
life and work.
Student B: You are Sir Lawrence Bragg. Greet James
Watson and ask him questions about his life and
work.
6 Role play: You are James Watson’s landlady.
Complain to him about the noise he makes when
he comes in late.
7 Role play: Act out the meeting between Sir Lawrence
Bragg and Francis Crick in Sir Lawrence’s office
described on page 26.
8 Write: Write a letter from Rosalind Franklin to
Maurice Wilkins saying why you don’t want to share
the results of your latest work. Explain that you need
these for the talk you will give in three weeks from
now.
9 Write and role play: Prepare a conversation between
Francis Crick and his wife Odile. Francis wants to
talk about his discoveries about Vand’s theories. Odile
wants to decide what to wear when they go out to the
Green Door. When you have done this, act out your
conversation.
10 Discuss: Crick says that Bill Cochran’s mathematical
system was shorter and ‘more elegant’ than his own.
Discuss the meaning of ‘elegant’ in this context.
Chapters 5–6, pages 30–45
After reading
11 Write: Imagine that Watson writes an informal letter
to Crick describing Rosy’s talk. Use the information
contained in their reported conversation on the train
on pages 31–34.
12 Role play: Choose to be James Watson or Rosalind
Franklin. You are being interviewed on breakfast TV
(so not too scientific!). Say why your method of study
of DNA structure is the best method. Say why the
other methods are useless.
Chapters 7–8, pages 45–57
After reading
13 Role play: You are a Cambridge friend of James
Watson. He calls you from Scotland on 2 January.
Ask him about his Christmas holiday in Scotland
and if he has enjoyed it.
14 Write: Write the letter that Watson receives from
Washington. Use the information on pages 47 and 48.
15 Write: Prepare the short report on developments
in the United States that Watson gives in Oxford.
Apologize for the fact that Pauling and Luria are
not present and explain why. Use the information
in Al Hershey’s letter.
16 Present: Deliver the short talk you prepared in
activity 15. Answer as many questions as you can.
Chapters 9–10, pages 58–68
After reading
17 Role play: Have students act out the scene between
Ava Helen Pauling and James Watson. Collect the
information you need from page 59.
18 Write: Share ideas and then write a letter to
Peter Pauling telling him a little about Cambridge.
Mention the beautiful buildings, the cold weather,
the cold houses and the horrible food. Tell Peter
that you know John Kendrew and that will do
everything you can to help him to survive his time in
Cambridge. Use the information in both Chapter 9
and Chapter 10. Remember to describe Cambridge
from an American point of view.
19 Role play: Role play the scene with the hostess at the
garden party on page 60.
20 Discuss: How do you feel about the way Watson
writes about Rosy on page 64? Is he justified or is
he unfair? Imagine, what Rosy would say about her
position if she was writing this book?
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21 Role play: Have students act out the scene of
Watson’s visit to the doctor on page 65.
Chapters 11–12, pages 68–85
After reading
22 Role play: Act out the scene in Maurice Wilkins’
office when Rosy tells him she wants to transfer back
to Bernal’s laboratory at Birkbeck College. Use the
information on pages 68 and 69.
23 Write and discuss: Describe the contents of Linus
Pauling’s paper and what you (James Watson) think is
wrong with it. Use the information on page 70.
24 Discuss: Linus Pauling sent two typed copies of his
paper: one to Lawrence Bragg and the other to his
son, Peter. This was in the days before photocopiers
and email. How would the story have been different
if all the characters had had access to these modern
technologies.
Chapters 13–15, pages 85–102
After reading
25 Role play: James Watson is working with a model of
DNA when Francis Crick comes into the lab. James
tells him about his idea about pairing A and T held
together with two hydrogen bonds and G and C held
together with two hydrogen bonds. James explains the
advantages, mentioning that this structure could
explain a much better copying scheme (see page 89).
26 Role play: Student A is Watson. Student B is Crick.
Have students work in pairs and act out the scene
between Watson and Crick at the pub on page 91.
27 Role play: Have students work in pairs and role play
the scene in which James Watson explains that the
typist at the Cavendish laboratory was not available,
and he asks his sister Elizabeth to type the 900-word
article. The students can take turns playing the role of
Watson.
Extra activities
28 Group work: Invite different groups of students
to research, using libraries and the Internet, either
Charles Darwin, Carl Linnaeus or Gregor Mendel.
Consider the life, ideas and achievements of each and
how this relates to the work of Crick and Watson.
Each group should prepare and deliver a short
presentation to the class on the selected scientist.
After the last presentation, the significance of these
individuals can be discussed in class.
29 Research: Find out more about Sir Lawrence Bragg
and his work in X-ray crystallography for which he
was awarded with the Nobel Prize in Physics in 1915.
Why did this make him a very suitable person to lead
the team searching for the structure of DNA?
30 Discuss: On 26 June 2000, after ten years’
international cooperation between scientists from
Europe, Japan, Britain and America, the first draft of
the genetic sequence of a typical human being was
announced by the Prime Minister of Britain and the
President of the United States. The sequence is called
the human genome and opens up endless possibilities.
Genes that carry inherited diseases, for example, may
be isolated and removed from a parent’s sperm or egg.
In the future parents may be able to design their own
children. Are these developments good ideas or are
they a dangerous interference with nature?
31 Discuss: Genetic engineering is the deliberate
alteration of the DNA of an organism in order to
change its character. This is already practised in many
areas, using DNA from one species to change another.
Genes from a fish that lives in very cold water, for
example, have been introduced into the DNA of a
tomato, so that the tomato can survive much colder
temperatures. Tomato growers will then be able to
extend their growing season and make more money.
Genes from a jellyfish have been introduced into pigs.
The piglets resulting from this cross had bright yellow
snouts and trotters, glowing in the dark as jellyfish
glow underwater. The point of this exercise was to
prove that modified genes could be used to grow
human organs, which could then be used in
transplant operations.
Once again, are these positive scientific developments,
or are they a dangerous interference with nature?
32 Artwork: On page 17, Watson describes a walk along
the river through King’s and Trinity colleges saying:
I had never seen such beautiful buildings in all my life.
Use books and the Internet to find photographs of
the beautiful buildings in Cambridge. Make a display
with notes for other students in your school.
33 Research and write: In 1962 John Watson, Francis
Crick and Maurice Wilkins were jointly awarded with
the Nobel Prize for Physiology or Medicine. Find out
more about Alfred Nobel and the Nobel Prize. Learn
more about winners of the Nobel Prize.
34 Research and write: Lawrence Bragg was born in
Australia in 1890. When he was five years old, he
fell off his tricycle and broke his arm. His father, a
great scientist William Henry Bragg had heard about
the work of Röntgen’s experiments with the newly
discovered X-rays. His father used X-ray’s to examine
his son’s arm (the first time this had been done in
Australia). Find out about Röntgen and his
discoveries. Have you ever had an X-ray? Tell your
friends about it.
35 Debate: Write this statement on the board: ‘Genetic
engineering is a good thing for the future of the
world.’ Take a class vote. Divide the class in two. One
half prepares arguments in favour, the other against.
There are some ideas in the Background and Themes
section above. Students present their arguments and
ask each other questions. Take a second class vote.
Has anyone changed their mind?
Vocabulary activities
For the Word List and vocabulary activities, go to
www.penguinreaders.com.