The document discusses the discovery of the structure of DNA. In 1953, James Watson and Francis Crick determined that DNA consists of two strands coiled around each other in a double helix formation. They were able to deduce this structure based on the work of Rosalind Franklin and Maurice Wilkins. Franklin's X-ray diffraction images, especially her Photo 51, provided key evidence of DNA's structure without which Watson and Crick's discovery would not have been possible. While all four scientists contributed to the discovery, only Watson, Crick, and Wilkins received a Nobel Prize in 1962 for their work.

1. The Story of DNA
AIS 2014

2. Questions everyone asks
Who am I?
Where did I come from?
How are we different from each other?
Will I get cancer?
What will my children look like?
Who was in this room an hour ago?
Why do I love who I love?

3. Feb 28, 1953
Two guys walk into a bar
and say they have the answer
to the secret of life itself….
What do you think, do they?

4. The discovery
of the structure of
the DNA
Double Helix
is one of the
greatest findings
of all time,
but it’s also one
of the most
controversial !!!!

5. KEY SCIENTISTS INVOLVED

6. James Watson Francis Crick
Rosalind Franklin
Maurice Wilkins

7. What is DNA?

8. DNA (Deoxyribonucleic Acid)
DNA is a double stranded
molecule that is twisted into a
Helix (Spiraling Staircase)
DNA Double Helix

9. Each strand consists of:
1) A Sugar Phosphate Backbone

10. Each strand consists of:
1) A Sugar Phosphate Backbone
2) Four Base Chemicals
(Attached in Pairs)

11. Soon after WWII the race to
discover the
“Secret of Life” was on.

12. VS
King’s College
Rosalind Franklin Maurice Wilkins
Cambridge University
James Watson Francis Crick
Caltech University
Linus Pauling

13. King’s College
• Rosalind Franklin accepts a job at King’s College to work in Maurice Wilkins’ Lab
• At the time of her arrival Wilkins is away on other matters
• When Wilkins returns, he discovers that his lab is taken over by Franklin
• He notices that Franklin is very intelligent and is able to work independently
• She spends hundreds of hours perfecting her X-ray Diffraction images and
hand written calculations
• Wilkins is still under the impression that Franklin is his assistant
• There is a lot of tension in the lab due to miscommunication and personality
clashes
King’s College
Franklin Wilkins

14. Franklin’s Life and Work

15. British chemist
Rosalind Franklin
is best known for
her role in the
discovery of the
structure of DNA,
and for her
pioneering use of
X-ray diffraction.

16. Claim to Fame
Determined the X-Ray
Structure of
DNA
In 1962 James Watson (b.
1928), Francis Crick (1916–
2004), and Maurice Wilkins
(1916–2004) jointly received the
Nobel Prize in physiology or
medicine for their 1953
determination of the structure of
deoxyribonucleic acid (DNA).

17. TWO FORMS OF DNA
In 1951 Rosalind Franklin discovers the Two Forms of DNA
through her X-ray diffraction images.
A – Dry Form B – Wet Form
Photo 51

18. X-Ray Crystallography

19. Watson and Crick’s Work

20. Watson and Crick’s Work
In 1951 James Watson traveled from the United States to work with
Francis Crick at Cambridge University
Watson and Crick used the “Model Building” approach
They physically built models out of wire, sheet metal, nuts and bolts to
come up with the structure of DNA
Why did they build models?
“Sometimes the fingers can grasp
what the mind cannot”
(Biology the Science of Life)

21. Social and Cultural Environment
• Science at the time was a male dominated field
• Women did not receive equal treatment
• Women were forbidden in the lunch room
• Franklin is unhappy at King’s College
• She has no one to share ideas and collaborate with
• She is fed up and decides to leave King’s College
But before she does, Franklin promises to finish writing up her research
papers
In the process of her move, Wilkins gets hold of Franklin’s work which
contained the famous photo 51

22. Rosalind Franklin’s Photo 51
Photo 51

23. How Watson and Crick Solved the DNA Structure
They already knew from Franklin and Wilkins’ work
that DNA was in the form of a Double Helix
Photo 51
They used Chargaff’s Rule to figure out how the 4 Bases
match up in pairs

24. How Watson and Crick Solved the DNA Structure
They discovered that:
• The Sugar-Phosphate Backbone
was on the outside
• Which protected the Bases on the
inside

25. “Nature”
Watson & Crick quickly published their work in the
Scientific Journal “Nature” on April 25th 1953

26. The Nobel Prize
• In 1962 Watson, Crick & Wilkins won the Nobel Prize for their
• discovery of the structure of DNA
• However, there is no mention of Franklin’s key work.