Watson and Crick By John Yogus February 27, 2004

Watson and CrickWatson and Crick

By John YogusBy John Yogus

February 27, 2004February 27, 2004

ImportantImportant

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James WatsonJames Watson

Young American Young American ScientistScientist

Strong interest in Strong interest in discovering the discovering the structure of DNA.structure of DNA.

Earned his bachelor’s Earned his bachelor’s degree at age 19 and degree at age 19 and his PhD at 22his PhD at 22

Francis CrickFrancis Crick

English scientistEnglish scientist

Worked at the Worked at the Cavendish LaboratoryCavendish Laboratory


In the early 1950s the race was on to In the early 1950s the race was on to discover the structure of DNA. discover the structure of DNA.

Watson traveled to Cambridge to study Watson traveled to Cambridge to study with Crick. with Crick.

Important OthersImportant Others

Other prominent figures were trying to discover the Other prominent figures were trying to discover the structure of DNA. structure of DNA.

These included Linus Pauling and Rosalind Franklin.These included Linus Pauling and Rosalind Franklin.

There was no connection between these people and There was no connection between these people and Watson and CrickWatson and Crick

Linus PaulingLinus Pauling

Pauling was an Pauling was an American chemist. American chemist.

Prior to Watson Prior to Watson going to London, going to London, Pauling beat Pauling beat Cavendish scientists Cavendish scientists in discovering the in discovering the structure of keratin.structure of keratin.

Rosalind FranklinRosalind Franklin

Franklin was an Franklin was an English scientist English scientist who worked at who worked at King’s College. She King’s College. She was an exemplary was an exemplary x-ray diffractionist.x-ray diffractionist.

True or FalseTrue or False

Pauling worked with Watson and Crick on Pauling worked with Watson and Crick on the discovery of the double helix.the discovery of the double helix.

TrueTrue FalseFalse

Working to DiscoveryWorking to Discovery

The framework for The framework for Watson and Crick’s Watson and Crick’s work was set forth work was set forth by earlier scientists by earlier scientists such assuch as

– Frederick GriffithFrederick Griffith– Oswald AveryOswald Avery– Hershey and Chase Hershey and Chase


• In 1951, Watson sat In 1951, Watson sat in on a conference in on a conference by Maurice Wilkins by Maurice Wilkins of King’s College of King’s College London. London.

• He was using X-ray He was using X-ray diffraction to study diffraction to study the structure of the structure of DNA. DNA.


• Crick and Wilkins were good friends. Crick and Wilkins were good friends. • However, Wilkins worked with Franklin However, Wilkins worked with Franklin

and these two were on bad terms. and these two were on bad terms. • Franklin was an accomplished Franklin was an accomplished

crystallographer. crystallographer. • She wouldn’t share info with Watson and She wouldn’t share info with Watson and

Crick Crick


Wilkins and Franklin worked at Kings College. Wilkins and Franklin worked at Kings College.


• Watson sat in on a seminar of Franklin’s. Watson sat in on a seminar of Franklin’s.

• He did not take notes on her lecture. He did not take notes on her lecture. • He erroneously began work on modeling He erroneously began work on modeling

the structure of DNA.the structure of DNA.• These efforts proved fruitless.These efforts proved fruitless.


• Watson and Crick temporarily gave up Watson and Crick temporarily gave up on their work. on their work.

• Watson studied tobacco mosaic virus Watson studied tobacco mosaic virus and Crick hemoglobin.and Crick hemoglobin.

• Click the red arrow below to see pictures Click the red arrow below to see pictures of the tobacco mosaic virus and of the tobacco mosaic virus and hemoglobin.hemoglobin.


• At this point, Watson and Crick endorsed At this point, Watson and Crick endorsed Franklin and Wilkins.Franklin and Wilkins.

• Franklin discovered that DNA could take Franklin discovered that DNA could take two forms, A and B. two forms, A and B.

• Franklin and Wilkins fought over this and Franklin and Wilkins fought over this and Franklin was awarded the A type and Franklin was awarded the A type and Wilkins the B type.Wilkins the B type.

• Click the red button below to see A and Click the red button below to see A and B forms of DNA.B forms of DNA.


• In the mean time, Watson and Crick’s In the mean time, Watson and Crick’s interest was still alive in DNA. interest was still alive in DNA.

• During their lapse, they tried to During their lapse, they tried to determine how Chargaff’s rule played determine how Chargaff’s rule played into the picture.into the picture.


• In December of 1952, it In December of 1952, it was suggested that was suggested that Pauling had come up Pauling had come up with the structure of with the structure of DNA. DNA.

• Watson and Crick Watson and Crick immediately knew this immediately knew this wasn’t the case after wasn’t the case after examining Pauling’s examining Pauling’s model.model.

• Pauling suggested a Pauling suggested a triple helix.triple helix.


• However, this put pressure on the two to However, this put pressure on the two to figure out the structure of DNA.figure out the structure of DNA.

• Pauling’s model provided many clues Pauling’s model provided many clues that would help others in their search.that would help others in their search.


• Watson went to London to warn Wilkins Watson went to London to warn Wilkins and Franklin. and Franklin.

• However, he and Franklin had a major However, he and Franklin had a major fall out. fall out.

• Just then, Wilkins walked into the lab and Just then, Wilkins walked into the lab and rescued Watson.rescued Watson.


• As the two walked As the two walked away, Wilkins away, Wilkins showed Watson a showed Watson a different picture of a different picture of a B DNA x-ray B DNA x-ray diffraction. diffraction.

• It was Photograph It was Photograph 51.51.

• A forms are on the A forms are on the left and B forms are left and B forms are on the right.on the right.


• At this point, At this point, Watson immediately Watson immediately knew the structure knew the structure of DNA had to be a of DNA had to be a helix.helix.


• Watson raced back to his Cavendish Watson raced back to his Cavendish Laboratory. Laboratory.

• There, he and Crick immediately began There, he and Crick immediately began building models of DNA.building models of DNA.


• In February of 1953, In February of 1953, Watson and Crick Watson and Crick invited Wilkins and invited Wilkins and Franklin to lunch. Franklin to lunch.

• From this meeting, From this meeting, Watson and Crick Watson and Crick obtained information obtained information that the strands of that the strands of DNA run in opposite DNA run in opposite directions. directions.

Fast FactFast Fact

Did you notice in the previous slide the Did you notice in the previous slide the letters A, T, G and C in the hexagons? letters A, T, G and C in the hexagons? They are symbols for the 4 nitrogenous They are symbols for the 4 nitrogenous bases used in DNA. They represent bases used in DNA. They represent Adenine, Thymine, Guanine and Cytosine. Adenine, Thymine, Guanine and Cytosine. Click on the names of the nitrogenous Click on the names of the nitrogenous bases above to hear the correct bases above to hear the correct pronunciation of their names. pronunciation of their names.


• This information This information helped, but the two helped, but the two were still unsure how were still unsure how the nitrogenous bases the nitrogenous bases paired up with each paired up with each other. other.

• Then, Watson Then, Watson remembered Chargaff’s remembered Chargaff’s rule.rule.

• His rule was based on His rule was based on the data to the left.the data to the left.


• Implementing Implementing Chargaff’s rule, he Chargaff’s rule, he concluded Adenine concluded Adenine and Thymine were and Thymine were paired together. paired together.

• Similarly, Guanine Similarly, Guanine and Cytosine were and Cytosine were also paired together.also paired together.


• This configuration also suggested a This configuration also suggested a mechanism for replication of DNA.mechanism for replication of DNA.


• On February 28, On February 28, 1953 Watson and 1953 Watson and Crick walked into Crick walked into the Eagle pub in the Eagle pub in London and London and announced they had announced they had “found the secret of “found the secret of life.”life.”

QuestionQuestion

Who were among the first people that Watson Who were among the first people that Watson and Crick shared their discovery with?and Crick shared their discovery with?

A)A) The International Genetic SocietyThe International Genetic Society

B)B) London DNA InstituteLondon DNA Institute

C)C) Biology faculty at King’s CollegeBiology faculty at King’s College

D)D) Cavendish Historic SocietyCavendish Historic Society

E)E) Drinking buddies at the local pubDrinking buddies at the local pub


This is what Watson This is what Watson and Crick discovered.and Crick discovered.

Click on the picture to Click on the picture to see this in animation.see this in animation.


• Watson and Crick Watson and Crick published a one published a one page letter in page letter in NatureNature on April 25, 1953 on April 25, 1953 that informed the that informed the public of their public of their findings.findings.


Watson and Crick, Watson and Crick, along with Wilkins, along with Wilkins, were awarded the were awarded the Noble Prize in 1962 Noble Prize in 1962 for their efforts. for their efforts.

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AcknowledgementsAcknowledgements

Time, February 17, 2003Time, February 17, 2003Watsoncrombie and CrickWatsoncrombie and CrickOhio State UniversityOhio State UniversityStanford UniversityStanford UniversityThe bicameral mindThe bicameral mindBBC NewsBBC NewsSKonlineSKonlineUniversity of GeorgiaUniversity of Georgia

AcknowledgementsAcknowledgements

Memorial University of NewfoundlandMemorial University of NewfoundlandThe Bacculaerate School for Global EducationThe Bacculaerate School for Global EducationCitrus CollegeCitrus CollegeUniversity of PennsylvaniaUniversity of PennsylvaniaUniversity of MiamiUniversity of MiamiJohn CashJohn CashDT Media LimitedDT Media LimitedPurdue UniversityPurdue UniversityKing’s CollegeKing’s College

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Watson and Crick By John Yogus February 27, 2004