1 jan 1928 ano - Fredrick Grifith
Descrição:
For this study, Griffith used two strains of Pneumococcus bacteria, type III-S and type II-R.
There is one major difference between these two types; the III-S strain has a smooth polysaccharide coat which makes it resistant to the immune system of mice, whereas the II-R strain lacks this coat and so will be destroyed by the immune system of the host.
For the first stage of the transforming principle experiment, Griffith showed that mice injected with III-S died but when injected with II-R lived and showed few symptoms.
The next stage showed that if the mice were injected with type III-S that had been killed by heat, the mice all lived, indicating that the bacteria had been rendered ineffective.
The interesting results came with the third part of the experiment, where mice were injected with a mixture of heat killed III-S and live II-R.
Interestingly enough, the mice all died, indicating that some sort on information had been passed from the dead type III-S to the live type II-R. Blood sampling showed that the blood of the dead mice contained both live type III-S and live type II-R bacteria.
Somehow the type III-S had been transformed into the type III-R strain, a process he christened the transforming principle.
Adicionado na linha do tempo:
Timeline of DNA
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