Which of the following is correct about H-bonding in nucleotide?

Options

A. A - T G - C
B. A - G T - C
C. G - T A - C
D. A - A T - T

Answer

To answer the question about hydrogen bonding in nucleotides, let's break down the concepts step by step.

### Step-by-Step Solution:

1. **Understanding Nucleotides**:
- Nucleotides are the building blocks of nucleic acids (DNA and RNA). Each nucleotide consists of a nitrogenous base (which can be a purine or pyrimidine), a pentose sugar, and a phosphate group.

2. **Types of Nitrogenous Bases**:
- There are two types of nitrogenous bases:
- **Purines**: Adenine (A) and Guanine (G)
- **Pyrimidines**: Cytosine (C), Thymine (T), and Uracil (U)

3. **Complementary Base Pairing**:
- In DNA:
- Adenine (A) pairs with Thymine (T) through **2 hydrogen bonds**.
- Guanine (G) pairs with Cytosine (C) through **3 hydrogen bonds**.
- In RNA:
- Adenine (A) pairs with Uracil (U) through **2 hydrogen bonds**.
- Guanine (G) pairs with Cytosine (C) through **3 hydrogen bonds**.

4. **Analyzing the Options**:
- Option 1: **Adenine bonds with Thymine** (in DNA) and **Adenine bonds with Uracil** (in RNA). This is correct.
- Option 2: **Adenine and Guanine** are both purines and do not bond with each other. This is incorrect.
- Option 3: **Guanine and Thymine** do not pair together in either DNA or RNA. This is incorrect.
- Option 4: **Adenine and Adenine** or **Thymine and Thymine** do not form complementary pairs. This is incorrect.

5. **Conclusion**:
- The correct statement about hydrogen bonding in nucleotides is that **Adenine pairs with Thymine** in DNA and **Adenine pairs with Uracil** in RNA, making Option 1 the correct answer.

### Final Answer:
The correct statement about hydrogen bonding in nucleotides is that adenine pairs with thymine in DNA and with uracil in RNA.

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