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.