Describe the experiments that established the identity of ‘transforming principles’ of Griffith.

Frederick Griffith established that there was a transforming principle in bacterial genetics. He proposed that information could be transferred between different strains of bacteria. He used two strains of Pneumococcus bacteria with type III-S and type II-R and he experimented on the mice model. The III-S strain has a smooth polysaccharide coat which resistant to the immune system of mice, but the II-R strain lacks this coat and so will be destroyed by the immune system of the animal.

In the first stage of the transforming principle experiment, the mice injected with III-S died and mice injected with II-R lived and showed some symptoms.

The second stage proved the mice injected with type III-S that had been killed by heat and the mice that lived indicated that the bacteria had been passed inefficiently.

In the third stage of the experiment, the mice were injected with a mixture of heat-killed III-S and live II-R. The mice all died, indicated the transaction of information passed to the dead type III-S to the live type II-R. Analysis of blood showed that the blood of the dead mice contained both live type III-S and live type II-R bacteria. Anyhow the type III-S had been transformed into the type III-R strain, a process he named the transforming principle.

Later this experiment was again conducted by scientists and they discovered that DNA was the mechanism for this transferal of genetic information between the two bacterial strains, as Griffith experiment this concept before DNA was explored.