The transforming principal in Griffith's experiment was established

Options

A. When live S-strain of s. Pneumoniae was injected into mice .
B. When live R-strain of s. Pneumoniae was injected into mice .
C. When heat killed R-strain of S.Pneumoniae was injected into mice
D. When mixture of heat killed S-strain and live R - strain of S. Pneumoniae was injected into mice

Answer

To solve the question regarding the transforming principle in Griffith's experiment, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding Griffith's Experiment**:
- Frederick Griffith conducted experiments in 1928 using two strains of *Streptococcus pneumoniae*: a virulent (disease-causing) strain (S strain) and a non-virulent (harmless) strain (R strain).

**Hint**: Remember the two strains involved: virulent (S) and non-virulent (R).

2. **Injection of Mice**:
- Griffith injected mice with different combinations of these strains:
- Live S strain (mice died)
- Live R strain (mice survived)
- Heat-killed S strain (mice survived)
- A mixture of heat-killed S strain and live R strain (mice died).

**Hint**: Note the outcomes of each injection to see how they relate to virulence.

3. **Observing Results**:
- The key observation was that when mice were injected with the mixture of heat-killed S strain and live R strain, they died. This was unexpected because neither the heat-killed S strain nor the live R strain alone caused death.

**Hint**: Focus on the unexpected result of the mixture causing death.

4. **Conclusion of the Experiment**:
- Griffith concluded that some "transforming principle" from the heat-killed S strain was taken up by the live R strain, transforming it into a virulent form. This indicated that genetic material was being transferred.

**Hint**: Think about what "transforming principle" means in the context of genetic material.

5. **Identifying the Correct Answer**:
- The question asks for the condition under which the transforming principle was established. The correct condition is when the mixture of heat-killed S strain and live R strain was injected into the mice.

**Hint**: Identify the specific combination that led to the transformation and subsequent death of the mice.

### Final Answer:
The transforming principle in Griffith's experiment was established when a mixture of heat-killed S strain and live R strain of *Streptococcus pneumoniae* was injected into the mice.