How many hydrogen bond present between A and T, G and C respectively :-

Options

A. 3,3
B. 2,3
C. 3,2
D. 2,3

Answer

To determine the number of hydrogen bonds present between adenine (A) and thymine (T), and between guanine (G) and cytosine (C), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Nitrogenous Bases**:
- In DNA, the nitrogenous bases are divided into two categories: purines and pyrimidines.
- Purines include adenine (A) and guanine (G).
- Pyrimidines include thymine (T) and cytosine (C).

2. **Determine the Pairing of Bases**:
- Adenine (A) pairs with thymine (T).
- Guanine (G) pairs with cytosine (C).

3. **Count the Hydrogen Bonds**:
- **Adenine (A) and Thymine (T)**:
- A and T are connected by **2 hydrogen bonds**.
- **Guanine (G) and Cytosine (C)**:
- G and C are connected by **3 hydrogen bonds**.

4. **Summarize the Findings**:
- Therefore, the number of hydrogen bonds between A and T is **2**.
- The number of hydrogen bonds between G and C is **3**.

5. **Final Answer**:
- The correct answer is: A and T have **2 hydrogen bonds**, and G and C have **3 hydrogen bonds**.