Heat killed S- cells alongwith live R- cells of Diplococcus pneumoniae were injected in mice

Options

A. Mice survived and had live S- cells
B. Mice survived and had dead R-cells
C. Mice died and showed live S- cells
D. Mice died and showed live R- cells.

Answer

**Step-by-Step Solution:**

1. **Understanding the Experiment**: The question refers to an experiment conducted by Frederick Griffith in 1928 involving *Diplococcus pneumoniae*, which is now known as *Streptococcus pneumoniae*. This experiment demonstrated the phenomenon of transformation in bacteria.

2. **Types of Bacteria**: In Griffith's experiment, there were two strains of *Diplococcus pneumoniae*:
- **S strain (Smooth)**: This strain is virulent (disease-causing) and has a smooth appearance due to its polysaccharide capsule.
- **R strain (Rough)**: This strain is non-virulent and has a rough appearance because it lacks the protective capsule.

3. **Initial Injections**:
- When mice were injected with live R strain, they survived because the R strain is non-virulent.
- When mice were injected with live S strain, they died due to the virulence of the S strain.

4. **Heat-Killed S Strain**: When Griffith injected mice with heat-killed S strain, the mice survived because the bacteria were dead and could not cause disease.

5. **Combination Injection**: The critical part of the experiment involves injecting mice with a mixture of heat-killed S strain and live R strain. The expectation was that the mice would survive since the S strain was heat-killed. However, the mice died.

6. **Conclusion of the Experiment**: Upon examination, it was found that the mice that died had live S cells in their bodies. This indicated that the live R strain had somehow taken up genetic material from the heat-killed S strain, transforming the non-virulent R strain into virulent S strain. This process is known as transformation.

7. **Correct Answer**: Based on the experiment, the correct option is that the mice died and showed live S cells (Option 3).