Which one of the following palindromic base sequences in DNA can be easily cut at about the middle by some particular restriction enzyme?

Options

A. 5'............ CGTTCG...........3'
3' ........... ATCGTA..........5'
B. 5'................ GATATG............3'
3'.......... CTACTA............5'
C. 5'..............GAATTC.............
3'...............CTACTA.............3'
D. none of the above

Answer

To determine which palindromic base sequence in DNA can be easily cut at about the middle by a particular restriction enzyme, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Restriction Enzymes**: Recognize that restriction enzymes, also known as molecular scissors, cut DNA at specific sequences known as palindromic sequences. These sequences read the same in both directions when considering complementary strands.

2. **Identify Palindromic Sequences**: A palindromic sequence in DNA is one that reads the same from the 5' to 3' direction on one strand and from the 3' to 5' direction on the complementary strand.

3. **Examine the Given Options**: We need to analyze each of the provided sequences to check if they are palindromic.

- **Option 1**: 5' - CGTTCG - 3'
- Complementary strand: 3' - GCAAGC - 5'
- Not palindromic.

- **Option 2**: 5' - GATATG - 3'
- Complementary strand: 3' - CTATA - 5'
- Not palindromic.

- **Option 3**: 5' - GAA TTC - 3'
- Complementary strand: 3' - CTT AAG - 5'
- Not palindromic.

- **Option 4**: 5' - GAATTC - 3'
- Complementary strand: 3' - CTTAAG - 5'
- This is palindromic as it reads the same in both directions.

4. **Conclusion**: Since only option 4 (5' - GAATTC - 3') is a palindromic sequence, it can be easily cut by a restriction enzyme, specifically EcoRI, which recognizes this sequence.

### Final Answer:
The correct option is **Option 4: GAATTC**.