When McLeod, Avery and McCarty experimented to establish the chemical nature of the Transforming Principle', which of the following statement/s helped them reach their conclusion?
1: Proteases did not affect transformation
2: DNases did not affect transformation,
3: RNases did not affect transformation.
4: The R strain could synthesise the polysaccharide coat.

Options

A. only 1 and 2
B. only 1 and 3
C. only 1, 3 and 4
D. only 2,3 and 4

Answer

To solve the question regarding the experiments conducted by McLeod, Avery, and McCarty to establish the chemical nature of the 'Transforming Principle', we need to analyze each of the statements provided and determine which ones contributed to their conclusions.

### Step-by-Step Solution:

1. **Understanding the Experiment**:
McLeod, Avery, and McCarty built upon Griffith's earlier work. They aimed to identify the substance responsible for the transformation of non-virulent R strain bacteria into virulent S strain bacteria.

2. **Analyzing Statement 1**:
- **Statement**: Proteases did not affect transformation.
- **Analysis**: Proteases break down proteins. If the transformation still occurred in the presence of proteases, it suggests that proteins are not the transforming principle. This statement supports the conclusion that proteins are not responsible for transformation.

3. **Analyzing Statement 2**:
- **Statement**: DNases did not affect transformation.
- **Analysis**: DNases degrade DNA. If DNases did not affect transformation, it would imply that DNA is not the transforming principle. However, in their experiments, the presence of DNases did inhibit transformation, indicating that DNA is indeed the transforming principle. Therefore, this statement does not support their conclusion.

4. **Analyzing Statement 3**:
- **Statement**: RNases did not affect transformation.
- **Analysis**: RNases degrade RNA. If RNases did not affect transformation, it suggests that RNA is not the transforming principle. In their experiments, the transformation still occurred in the presence of RNases, supporting the conclusion that RNA is not responsible for the transformation.

5. **Analyzing Statement 4**:
- **Statement**: The R strain could synthesize the polysaccharide coat.
- **Analysis**: This statement is somewhat misleading. The R strain does not naturally synthesize the polysaccharide coat; it is the S strain that possesses this capability. This statement does not contribute to the conclusion about the transforming principle.

### Conclusion:
Based on the analysis:
- **Correct Statements**: 1 (Proteases did not affect transformation) and 3 (RNases did not affect transformation) are correct and helped McLeod, Avery, and McCarty conclude that DNA is the transforming principle.
- **Incorrect Statement**: 2 (DNases did not affect transformation) is incorrect as DNases did affect transformation, and 4 (The R strain could synthesize the polysaccharide coat) is misleading.

### Final Answer:
The statements that helped them reach their conclusion are **1 and 3**.

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