In which of the following case, mice will remain alive in Griffith's transforming experiments ?

Options

A. Heat killed S - strain injected into mice .
B. DNA from heat killed S - strain + R - strain injected into mice .
C. S - strain injected into mice.
D. More than one option is correct

Answer

To determine in which case the mice will remain alive in Griffith's transforming experiments, we need to analyze the different scenarios presented in the question based on Griffith's original experiments with Streptococcus pneumoniae.

### Step-by-Step Solution:

1. **Understanding the Strains**:
- Griffith worked with two strains of Streptococcus pneumoniae:
- **S strain (smooth)**: This strain is pathogenic and causes pneumonia in mice.
- **R strain (rough)**: This strain is non-pathogenic and does not cause disease in mice.

2. **Analyzing the Options**:
- **Option 1**: Heat-killed S strain injected into mice.
- Since the S strain is heat-killed, it loses its pathogenicity. Therefore, the mice will remain alive.
- **Option 2**: DNA from heat-killed S strain plus R strain injected into mice.
- The DNA from the heat-killed S strain can transform the R strain into a pathogenic form, leading to the death of the mice.
- **Option 3**: S strain injected into mice.
- The S strain is pathogenic, so the mice will die.
- **Option 4**: More than one option is correct.
- Based on the analysis, only Option 1 is correct.

3. **Conclusion**:
- The only scenario in which the mice will remain alive is when the heat-killed S strain is injected into the mice (Option 1).

### Final Answer:
**The mice will remain alive in Griffith's transforming experiments when the heat-killed S strain is injected into them (Option 1).**