Select the base which is not common in DNA and RNA.

Options

A. Adenine (A)
B. Guanine (G)
C. Cytosine (C)
D. Uracil (U)

Answer

To solve the question of identifying the base that is not common in DNA and RNA, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of Nucleic Acids**:
- Nucleic acids, which include DNA and RNA, are made up of three components: a pentose sugar, a phosphate group, and nitrogenous bases.

2. **Identify the Types of Nitrogenous Bases**:
- Nitrogenous bases are categorized into two types: purines and pyrimidines.
- **Purines**: Adenine (A) and Guanine (G).
- **Pyrimidines**: Cytosine (C), Thymine (T), and Uracil (U).

3. **List the Bases Present in DNA**:
- The bases found in DNA are Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

4. **List the Bases Present in RNA**:
- The bases found in RNA are Adenine (A), Uracil (U), Guanine (G), and Cytosine (C).

5. **Compare the Bases**:
- Common bases in both DNA and RNA: Adenine (A), Guanine (G), and Cytosine (C).
- Bases that are not common: Thymine (T) is found in DNA but not in RNA, and Uracil (U) is found in RNA but not in DNA.

6. **Select the Answer**:
- The question asks for the base that is not common in DNA and RNA. The bases that fit this criterion are Thymine (T) and Uracil (U).
- Since the question specifies to select one base, Uracil (U) is the correct answer as it is only present in RNA.

### Final Answer:
- The base which is not common in DNA and RNA is **Uracil (U)**.