Download - The story of DNA modified by Karobi Moitra
The Story of DNA
AIS 2014
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?
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?
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 !!!!
KEY SCIENTISTS INVOLVED
Rosalind Franklin
James Watson Francis Crick
Maurice Wilkins
What is DNA?
DNA (Deoxyribonucleic Acid)
DNA is a double stranded molecule that is twisted into a Helix (Spiraling Staircase)
DNA Double Helix
Each strand consists of:
1) A Sugar Phosphate Backbone
Each strand consists of:
2) Four Base Chemicals (Attached in Pairs)
1) A Sugar Phosphate Backbone
Soon after WWII the race to discover the
“Secret of Life” was on.
VS
James Watson Francis Crick
Cambridge University
Rosalind Franklin Maurice Wilkins
King’s College
Caltech University
Linus Pauling
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
Franklin Wilkins
King’s College
Franklin’s Life and Work
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.
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).
In 1951 Rosalind Franklin discovers the Two Forms of DNA through her X-ray diffraction images.
A – Dry Form B – Wet Form
TWO FORMS OF DNA
Photo 51
X-Ray Crystallography
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)
Watson and Crick’s Work
• 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
Social and Cultural Environment
Rosalind Franklin’s Photo 51
Photo 51
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
They used Chargaff’s Rule to figure out how the 4 Bases match up in pairs
Photo 51
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
Watson & Crick quickly published their work in the Scientific Journal “Nature” on April 25th 1953
“Nature”
• In 1962 Watson, Crick & Wilkins won the Nobel Prize for their • discovery of the structure of DNA
The Nobel Prize
• However, there is no mention of Franklin’s key work.