Which amongst the following was the first restriction endonuclease enzyme used ?

Options

A. Barn HI
B. Sma I
C. Eco RI
D. Hind II

Answer

To determine which amongst the following was the first restriction endonuclease enzyme used, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Restriction Endonucleases**:
- Restriction endonucleases, also known as restriction enzymes, are proteins that cut DNA at specific sequences. They are often referred to as "chemical knives" because of their ability to cleave DNA.

2. **Identify the Options**:
- The options provided are:
- A) BamH1
- B) Smar1
- C) EcoR1
- D) Hinc2

3. **Research Historical Context**:
- The first restriction enzyme to be discovered and used in molecular biology was EcoR1, which was isolated from the bacterium *Escherichia coli*.

4. **Analyze the Options**:
- Based on historical data, EcoR1 is known to be the first restriction endonuclease enzyme that was characterized and used in research.

5. **Conclusion**:
- Therefore, the correct answer to the question is **C) EcoR1**.