Which of the following nitrogen base is not found in DNA -

Options

A. Thymine
B. Cytosine
C. Guanine
D. Uracil

Answer

To determine which nitrogen base is not found in DNA, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of DNA**:
- DNA (Deoxyribonucleic Acid) is a polymer made up of deoxyribonucleotides.
- Each deoxyribonucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

2. **Identify the Nitrogenous Bases in DNA**:
- The nitrogenous bases in DNA are categorized into two groups: purines and pyrimidines.
- **Purines**: Adenine (A) and Guanine (G).
- **Pyrimidines**: Cytosine (C) and Thymine (T).

3. **List the Nitrogen Bases Found in DNA**:
- Therefore, the nitrogen bases present in DNA are Adenine, Guanine, Cytosine, and Thymine.

4. **Examine the Given Options**:
- The options provided include Thymine, Cytosine, Guanine, and Uracil.
- From our previous identification, Thymine, Cytosine, and Guanine are all found in DNA.

5. **Identify the Base Not Found in DNA**:
- Uracil is the nitrogen base that is not found in DNA. Instead, it is found in RNA (Ribonucleic Acid).

6. **Conclusion**:
- The nitrogen base that is not found in DNA is **Uracil**.

### Final Answer:
- The nitrogen base not found in DNA is **Uracil**.