Which one of the following represents a palindromic sequence in DNA?

Options

A. 5' - GAATTC - 3'
3' - CTTAAG - 5'
B. 5' - CCAATG - 3'
3' - CAATCC - 5'
C. 5' - CATTAG - 3'
3' - GATAAC - 5'
D. 5' - GATACC - 3'
3' - CCTAAG - 5'

Answer

To determine which of the given DNA sequences represents a palindromic sequence, we need to follow these steps:

### Step-by-Step Solution:

1. **Understand Palindromic Sequences**: A palindromic sequence in DNA is one that reads the same in the 5' to 3' direction on one strand and in the 5' to 3' direction on the complementary strand when read in reverse.

2. **Analyze the First Sequence**:
- Given sequence: 5' G A A T T C 3'
- Complementary sequence (reverse): 3' C T T A A G 5'
- When read from 5' to 3' on the complementary strand, it reads: 5' G A A T T C 3' (same as the original).
- **Conclusion**: This is a palindromic sequence.

3. **Analyze the Second Sequence**:
- Given sequence: 5' C C A A T G 3'
- Complementary sequence (reverse): 3' G G T T A C 5'
- When read from 5' to 3' on the complementary strand, it reads: 5' C A A T G 3' (not the same as the original).
- **Conclusion**: This is not a palindromic sequence.

4. **Analyze the Third Sequence**:
- Given sequence: 5' C A T T A G 3'
- Complementary sequence (reverse): 3' G T A A T C 5'
- When read from 5' to 3' on the complementary strand, it reads: 5' G A T T A C 3' (not the same as the original).
- **Conclusion**: This is not a palindromic sequence.

5. **Analyze the Fourth Sequence**:
- Given sequence: 5' G A T A C C 3'
- Complementary sequence (reverse): 3' C T A G G 5'
- When read from 5' to 3' on the complementary strand, it reads: 5' C C T A G 3' (not the same as the original).
- **Conclusion**: This is not a palindromic sequence.

### Final Conclusion:
The only palindromic sequence among the options provided is the first one: **5' G A A T T C 3'**.

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