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DISCOVERY OF DNA
Structure and Function

Ancient Ideas on Genetics
Father of Modern Genetics

Gregor Mendel
(1822-1884)
Fred Griffith’s Transforming
Principle (1928)
•
Experimented with two strains of Pneumococcus bacteria
Smooth:
S- strain
With capsule
Rough:
R-strain
No capsule
Heat –killed
S-strain

Combine live R-strain with Heat-killed
S-strain
Where is the Conveyer of Inheritance
(transforming principle)? Protein or DNA

Thomas Morgan
(1911)
Oswald Avery et al. (1944)

1.
2.
The Experiment
Treated the bacteria with
centrafugation, which eliminates large
cellular pieces.
Added protease, which removes all
proteins
The result:
3. Treated with deoxyribonuclease, which
eliminates all DNA
The result:
Alfred Hershey-Martha Chase
Experiment (1952)



Use Radioactively
labeled viruses
2 types
How can they be
used to discover
what is the
conveyer of
inheritance?
32P
35S
DNA or Protein????

http://highered.mcgrawhill.com/olc/dl/120076/bio21.swf
STRUCTURE OF DNA


Miescher (1869) looked at pus cells
Levene (1928)


Different types
of nucleotides:
A, T, G, C
What is the
implication of
this structure?
Erwin Chargaff (1949)
Rosalind Franklin (1950s)

Implications?
Watson and Crick 1953



Read the Nature article by Watson &
Crick
Discuss how they used the work of
others to come up with the structure of
DNA.
How does the structure account for
identical replication of DNA to be the
conveyer of inheritance?