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'______ATGGTA____5'
B. 5' _____GATATG____3'
3'______CTACTA____5'
C. 5' _____GAATTC____3'
3'______CTTAAG____5'
D. 5' _____CACGTA____3'
3'______CTCAGT____5'

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 Palindromic Sequences**: A palindromic sequence in DNA is a sequence that reads the same in both directions on complementary strands. For example, if one strand has the sequence 5' - GAA TTC - 3', the complementary strand would have the sequence 3' - CTT AAG - 5'.

2. **Identify the Restriction Enzyme**: The restriction enzyme mentioned in the question is EcoRI. This enzyme recognizes specific palindromic sequences and cuts the DNA at specific sites.

3. **Locate the EcoRI Recognition Site**: EcoRI recognizes the palindromic sequence 5' - GAA TTC - 3' and cuts between the G and A on both strands. This means it will cut the sequence as follows:
- On the top strand: 5' - G|AA TTC - 3'
- On the complementary strand: 3' - CTT|AA G - 5'

4. **Determine the Cut Location**: The cut occurs between the bases G and A in the sequence GAA TTC, which is approximately in the middle of the palindromic sequence.

5. **Conclusion**: Since EcoRI can cut the palindromic sequence 5' - GAA TTC - 3' at the middle, the answer to the question is that this sequence can be easily cut by the EcoRI enzyme.

### Final Answer:
The palindromic base sequence that can be easily cut at about the middle by the restriction enzyme EcoRI is:
**5' - GAA TTC - 3' and its complementary strand 3' - CTT AAG - 5'**.