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

Options

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

Answer

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

### Step 1: Understand the Composition of DNA
DNA (deoxyribonucleic acid) is a polymer made up of deoxyribonucleotides. Each deoxyribonucleotide consists of three components: a phosphate group, a deoxyribose sugar, and a nitrogenous base.

### Step 2: Identify the Nitrogenous Bases in DNA
The nitrogenous bases in DNA are classified into two categories:
- **Purines**: Adenine (A) and Guanine (G)
- **Pyrimidines**: Thymine (T) and Cytosine (C)

### Step 3: Compare with Other Nitrogenous Bases
In addition to the bases found in DNA, there is another nitrogenous base called Uracil (U), which is found in RNA (ribonucleic acid) instead of Thymine.

### Step 4: Conclusion
Since Uracil is not present in DNA and is replaced by Thymine in DNA, we can conclude that the nitrogen base that is not found in DNA is **Uracil (U)**.

### Final Answer:
The nitrogen base that is not found in DNA is **Uracil (U)**.

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