Step 1: Background of Griffith’s experiment.
Frederick Griffith's 1928 experiment demonstrated bacterial transformation using Streptococcus pneumoniae. The experiment involved two strains: the virulent Smooth (S) strain with a capsule, and the non-virulent Rough (R) strain lacking a capsule.
Step 2: Effects of different strains on mice.
- Living R strain: Mice survived due to its non-virulent nature.
- Heat-killed S strain: Mice survived as heat destroyed virulent factors.
- Living S strain: Caused death of mice due to its virulence.
Step 3: Key transformation principle.
When heat-killed S strain was combined with living R strain, the R strain absorbed DNA from the S strain.
This process transformed the R strain into the virulent S strain, resulting in the death of the mice.
Step 4: Conclusion.
The mixture of heat-killed S strain and living R strain proved lethal to mice.