Frederick Griffith (1928)
Steps of the Experiment
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What he concluded...
- He postulated that a substance from dead type S bacteria was "transforming" the type R bacteria into type S bacteria, Griffith called this process transformation
- Newly transformed bacteria (R from S) has acquired info to make capsule from the heat killed cells.
- Information replicated during replication and transmission occurred during cell division.
- Variation existed between capsule producing strain (S) and non-capsule (R strain).
- Conclusion: genetic material from heat-killed S type had been transferred to living R type and provided a new trait.
- Something in the virulent S strain could transform nonvirulent R strain bacteria into lethal form, even when S strain bacteria had been killed by high temp.
- These observation of "transformation" also meets the 4 criteria for the genetic material described before in the DNA section.
- At this point we still don't know what the transforming material is …