The document summarizes the key discoveries that led to determining the double helix structure of DNA. It describes early work in isolating and studying nucleic acids. It then explains Chargaff's rules of base pairing and the experiments proving DNA is the genetic material. The document outlines Linus Pauling's incorrect triple helix model of DNA structure and describes how in 1953, Watson and Crick published their landmark paper revealing the correct double helix structure of DNA, based on evidence including Photo 51. Watson, Crick and Wilkins were later awarded the Nobel Prize for this revolutionary discovery.

1. THE DOUBLE
HELIX:
TALE OF THE MOST
REVOLUTIONARY DISCOVERY
ADITHYA P BALAKRISHNAN
Reg. No: 04-AGRMA-01724-2018
M. Sc (Agri.) II Year
Dept. of Genetics and Plant Breeding

2. THE SECRET OF LIFE
■ Deoxyribonucleic acid: The
molecule carries our genetic
blue print.

3. Journey towards the double helix structure
Johann Friedrich Miescher
(1868)
 Isolated an acidic substance from human pus cells
Nuclein
 Altman: term Nucleic acid
Phoebus Levene
(1869-1940)
 Levene’s polynucleotide model

4. Chargaff’s Rule of base pairing
■ Amount of Adenine = amount of
Thymine
■ Amount of Guanine = amount of
cytosine
■ A+G =T+C

5. DNA stores the genetic information
F. Griffith’s experiment (1928)
The transforming principle
Alfred Hershey & Martha Chase (1952)
Universal acceptance of DNA as genetic material
Nobel-1969

6. Pauling’s triple helix model
■ Proposed in early 1952
■ Phosphate in the middle and bases
radiating outwards
Linus Pauling

7. The Four Major Players
On April 25, 1953: Watson & Crick published their paper in British journal Nature
Watson, Crick and Wilkins awarded Nobel for medicine 1962.

8. The Photo 51: Clue to the mystery

9. References
 Pray, L. (2008) Discovery of DNA structure and function:Watson and Crick.
Nature Education 1(1):100
 D. Peter Snustard and M. J Simmons. (2010). Principles of genetcs:Wiley
Publications