Discovery of the Double Helix - rio.edu Franklin (1920 - 1958) •England •PhD Physical Chemistry •France-coal •X-ray diffraction •Kings College •DNA - A and B form •Birkbeck
Rosalind Franklin (1920 - 1958)•England•PhD Physical Chemistry•France-coal•X-ray diffraction•Kings College •DNA - A and B form•Birkbeck College•Tobacco Mosaic Virus•Aaron Klug
X-ray diffraction
DNA Crystal
X-rays
film
Photo51
Raymond Gosling (1926 -)
•PhD student•Kings College•Wilkins/Franklin
Linus Pauling (1901-1994)
•Cal Tech•Chemist•Protein model
Peter Pauling (1931-2003)
•Son•Cavindish Lab
Erwin Chargaff (1905-2002)
•England•Chemist•Chargaff’s Rules•%G=%C•%A=%T
DNA Model
• Based on all above, Watson and Crick developed double helix model of DNA
• 2 strands running anti-parallel• G pairing with C• A pairing with T
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DNA Structure
Sugar
GP O1’
5’
Sugar
AP O1’
5’
Sugar
TP O1’
5’
Sugar
C PO
1’5’
Sugar
T PO
1’5’
Sugar
A PO
1’5’
antiparrallel strands
5’
3’
3’
5’
hydrogenbonding
Base Pairing
Guanine
Adenine
O
N
N
O
N
O
O
CH3
Thymine
N NH
HH
CytosineH
H
N H N
HH
HydrogenBonds
Double Helix
• One complete turn 34 A• 20 A diameter• 3.4 A between pairs• A = 10-8 m
25
Publication NatureApril 1953
Nobel Prize 1962Watson, Crick, Wilkins
The Double Helix 1967by James Watson
Other Books• What Mad Pursuit - Francis Crick• The Third Man of the Double Helix -
Maurice Wilkins• The Dark Lady of DNA - Brenda
Maddox• Avoid Boring People - James Watson• DNA - James Watson