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

Options

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

Answer

To solve the question "Which one of the following represents a palindromic sequence in DNA?", we need to understand the concept of palindromic sequences in DNA and analyze the given options. Here’s a step-by-step solution:

### Step 1: Understand the Definition of Palindromic Sequences
A palindromic sequence in DNA is a sequence that reads the same in both directions on complementary strands. This means that if you take one strand from 5' to 3', the complementary strand (3' to 5') should read the same sequence in reverse.

### Step 2: Analyze Each Option
We will examine each option provided to identify if it is palindromic.

1. **Option 1: C-A-T-T-A-G**
- 5' to 3': C-A-T-T-A-G
- 3' to 5': G-A-T-T-A-C
- **Analysis**: This does not read the same in both directions. (Not a palindrome)

2. **Option 2: G-A-T-A-C-C**
- 5' to 3': G-A-T-A-C-C
- 3' to 5': C-C-T-A-G
- **Analysis**: This does not read the same in both directions. (Not a palindrome)

3. **Option 3: G-A-A-T-T-C**
- 5' to 3': G-A-A-T-T-C
- 3' to 5': C-T-T-A-A-G
- **Analysis**: This reads the same in both directions. (Palindrome)

4. **Option 4: C-C-A-A-T-G**
- 5' to 3': C-C-A-A-T-G
- 3' to 5': C-T-A-A-G
- **Analysis**: This does not read the same in both directions. (Not a palindrome)

### Step 3: Identify the Correct Option
From the analysis, only **Option 3: G-A-A-T-T-C** is a palindromic sequence because it reads the same on both strands.

### Conclusion
The correct answer is **Option 3: G-A-A-T-T-C**, which is a palindromic sequence in DNA and is also the recognition site for the restriction enzyme EcoR1.

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