Question

Which of the following Streptococcus cells can kill mice?

• A. Living rough R strain
• B. Heat killed smooth S strain
• C. Heat killed smooth S strain and living rough R strain combination
• D. Heat killed rough R strain

Hint:

Griffith’s experiment demonstrated bacterial transformation: DNA is the genetic material responsible for heredity.

Answer 1

The Correct Option is C

Step 1: Background of Griffith’s experiment.
The famous Frederick Griffith experiment in 1928 showed the principle of transformation in bacteria using Streptococcus pneumoniae.
There are two types of strains: Smooth (S) strain with a capsule that is virulent and Rough (R) strain without a capsule that is non-virulent.
Step 2: Effects of different strains on mice.
- Living R strain: Non-virulent, so the mice survive.
- Heat killed S strain: Virulent factors are destroyed by heat, so the mice survive.
- Living S strain: Virulent and causes death of mice.
Step 3: Key transformation principle.
When heat killed S strain is mixed with living R strain, the DNA of S strain is taken up by R strain.
This transformation converts R strain into virulent S strain, which kills the mice.
Step 4: Conclusion.
Therefore, the combination of heat killed S strain and living R strain is lethal to mice.