Question

What was Griffith hypothesis?

Answer 1

Griffith hypothesis:

1. It was reported in the year 1928 by Frederick Griffith.
2. According to Griffith’s hypothesis, there was a transforming principle, which got transformed into the R-strain from the heat-killed S strain and made it virulent.
3. This genetic transformation was due to a process called Transformation.
4. For this experimental study, Griffith used two strains of pneumococcus that affect mice.
5. Of which the type III-S (rough)- virulent and type-II-R strain(rough)-is nonvirulent.
6. Later it was verified by Avery, McLeod, and McCarty.

Experiment:

1. Griffith injected both S and R strains to mice.
2. The one which was infected with the S strain developed pneumonia and died while that infected with the R strain stayed alive.
3. In the second stage, Griffith heat-killed the S strain bacteria and injected into mice, but the mice stayed alive.
4. Then, he mixed the heat-killed S and live R strains.
5. This mixture was injected into mice and they died. In addition, he found living S strain bacteria in dead mice.
6. Based on the observation, Griffith concluded that R strain bacteria had been transformed by S strain bacteria.
7. The R strain inherited some ‘transforming principle’ from the heat-killed S strain bacteria which made them virulent.
8. And he assumed this transforming principle as genetic material.