Which of the following is an incorrect statement?

Options

A. Chemically, adenine is 6 amino purine
B. Cytosine and adenine are purine bases
C. Two DNA strands are antiparallel due to hydrogen bonds holding them together
D. Pitch of dsDNA is 3.4 nm

Answer

To solve the question of identifying the incorrect statement among the given options, we can follow these steps:

### Step 1: Analyze Each Statement
1. **Statement 1**: "Chemically, Adenine is 6-Aminopurine."
- **Analysis**: This statement is correct. Adenine is indeed known as 6-Aminopurine because it has an amino group at the 6th position of the purine structure.

2. **Statement 2**: "Cytosine and Adenine are Purine bases."
- **Analysis**: This statement is incorrect. Adenine is a purine, but Cytosine is a pyrimidine. Therefore, this statement is false.

3. **Statement 3**: "2 strands of DNA are anti-parallel because of the hydrogen bond which holds them together."
- **Analysis**: This statement is partially correct. While the strands are indeed anti-parallel, it is primarily the orientation of the sugar-phosphate backbone and the phosphodiester bonds that cause the anti-parallel arrangement, not just the hydrogen bonds.

4. **Statement 4**: "Our double-stranded DNA has a pitch of 3.4 nm."
- **Analysis**: This statement is correct. The double helix of DNA has a pitch of approximately 3.4 nm, which corresponds to the distance of one complete turn of the helix.

### Step 2: Identify the Incorrect Statement
Based on the analysis:
- Statement 1 is correct.
- Statement 2 is incorrect (Cytosine is not a purine).
- Statement 3 is correct but needs clarification.
- Statement 4 is correct.

Thus, the incorrect statement is **Statement 2**: "Cytosine and Adenine are Purine bases."

### Final Answer
The incorrect statement is **Statement 2**.

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