Question

In Griffith's experiment, which of the following resulted in the death of the mice?

• A. Live S-strain bacteria $\to$ Injected into mice
• B. Live R-strain bacteria $\to$ Injected into mice
• C. Heat-killed S-strain bacteria$\to$ Injected into mice
• D. Heat-killed R-strain bacteria $\to$ Injected into mice

Answer 1

The correct option is A Live S-strain bacteria $\to$ Injected into mice

Griffith performed the transformation experiment in mice using the R and S strains of Streptococcus pneumoniae. S-strain is generally pathogenic and R-strain is non-pathogenic. However, heat-killed S-strain cannot cause the disease. So, when R-strain and heat-killed S-strain bacteria were injected separately, the mice stayed alive. But when injected together, the mice died. This was because R-strain bacteria got “transformed” into S-strain, and caused the disease. Heat-killed R-strain does not affect the mice and the mice lived.