Which of the following represents a correct palindromic sequence recognised by EcoRI ?

Options

A. `5'-overset(darr)(GA)"ATTC"-3'`
`5'-"CTTA"underset(uarr)(AG)-3'`
B. `5'-overset(darr)"CCCGGG"-3'`
`3'-underset(uarr)("GGGCCC")-5'`
C. `5'-overset(darr)(GA)"ATTC"-3'`
`3'-"CTTA"underset(uarr)(AG)-5'`
D. `5'-"ATGC"overset(darr)(CG)-3'`
`3'-"TACG"underset(uarr)(overlineGC)-5'`

Answer

To determine the correct palindromic sequence recognized by EcoRI, we need to follow these steps:

### Step-by-Step Solution:

1. **Understand EcoRI**: EcoRI is a restriction endonuclease that recognizes a specific palindromic DNA sequence. A palindromic sequence reads the same in both directions when considering the complementary strands.

2. **Identify the EcoRI Recognition Sequence**: The recognition sequence for EcoRI is:
- 5' - G A A T T C - 3'
- The complementary strand would be:
- 3' - C T T A A G - 5'

3. **Check the Options**: We will analyze the given options to find the one that matches the EcoRI recognition sequence.

- **Option A**: 5' - G A A T T C - 3' and 5' - G A A T T C - 3'
- This is incorrect because both strands should be complementary and in opposite orientations.

- **Option B**: 5' - C C C - 3'
- This is incorrect as it does not match the EcoRI recognition sequence.

- **Option C**: 5' - G A A T T C - 3' and 3' - C T T A A G - 5'
- This is correct as it represents the EcoRI recognition sequence in a palindromic manner.

- **Option D**: Starts with A
- This is incorrect as it does not match the EcoRI recognition sequence.

4. **Conclusion**: The correct palindromic sequence recognized by EcoRI is found in **Option C**.

### Final Answer:
**Option C: 5' - G A A T T C - 3' and 3' - C T T A A G - 5'**