Fredrick Griffith’s Experiment

Fredrick Griffith’s Experiment
Introduction
Fred Griffith in 1928 provided the evidence of hereditary material in bacteria.
Experimental Material
He was working on strains of streptococcus pneumoniae, which occurs in two distinct different forms.
R-Type
Rough surfaced, non-capsulated bacteria, without the capability of producing pneumonia.
Example
Smooth surfaced, capsulated bacteria with the capability of producing pneumonia i.e. virulent.
Steps of Experiment
1. He observed that, when he injected R-type bacteria in the mice, there was no ill effect.
2. When he injected the S-type, they proved to be fatal.
3. He also observed, when he injected both the bacteria separately after killing them by heating under high temperature, the mice did not develop the disease.
4. He also observed that when the injected the living R-type with heat killed S-type there was high mortality among the mice.
Conclusion
Fred Griffith concluded that the R-type bacteria gained genetic property of S-type inactive bacteria when they kept together, so R-type bacteria converted into virulent S-type by the activity of DNA. Hence by this experiment, it can be proved that DNA is a genetic material.