Question

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

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

Answer 1

The correct option is A

Live S strain bacteria $\to$ Inject 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 strains, and caused the disease. Heat-killed R strain has no effect on the mice and the mice live.