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Griffith’s work on
Pneumococcus
Frederick Griffith (1920) was a
medical officer in London. He was
looking for a way to fight pneumonia
in the epidemics after World War I.
The discovery was made as he heated
to 60°C instead of 100°C, killing the
pneumococcus bacteria but not
destroying their DNA. This scientist
changed genetics.
pneumococcus
bacteria
Pneumococcus bacteria
- a kind of Streptococcus bacteria
- cause severe pneumonia, meningitis,
septicaemia, and ear infections.
Rough form of
Pneumococcus
Smooth form of
Pneumococcus
What was Griffith’s experiment about?
After the experiment, Frederick Griffith drew
out two hypotheses :
1. The dead S strain had been
reanimated/resurrected.
2. The Live R had been transformed into Live
S by some "transforming factor"
Transformation Principle
Further experiments led Griffith to
conclude that number 2 was correct.
In 1944, three other scientists
revisited Griffith's experiment and
concluded the transforming factor was
DNA.
Helix structure of
DNA
- The End -