Which of the following statements is correct

Options

A. Adenine pairs with thymine through two H-bonds
B. Adenine pairs with thymine through one H-bond
C. Adenine pairs with thymine through three H-bonds
D. Adenine does not pair with thymine

Explanation

To determine which statement is correct regarding the pairing of adenine and thymine in DNA, let's analyze the information provided step by step.

### Step-by-Step Solution:

1. **Identify the Nitrogenous Bases**:
- In DNA, there are four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Among these, adenine pairs with thymine.

2. **Understand Base Pairing**:
- Adenine (A) pairs with thymine (T) through hydrogen bonds. This is a fundamental concept in molecular biology regarding DNA structure.

3. **Count the Hydrogen Bonds**:
- The specific pairing between adenine and thymine involves the formation of hydrogen bonds. It is known that adenine and thymine are connected by **two hydrogen bonds**.

4. **Evaluate the Statements**:
- **Statement 1**: "Adenine pairs with thymine through 2 hydrogen bonds." - This statement is correct.
- **Statement 2**: "Adenine pairs with thymine through three hydrogen bonds." - This statement is incorrect; the pairing involves two, not three.
- **Statement 3**: "Adenine does not pair with thymine at all." - This statement is also incorrect, as adenine does pair with thymine.

5. **Conclusion**:
- The only correct statement is that adenine pairs with thymine through **two hydrogen bonds**.

### Final Answer:
The correct statement is: **Adenine pairs with thymine through 2 hydrogen bonds.**

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