In DNA, uracil is replaced by

Options

A. Thymine
B. Thamine
C. Cytosine
D. Adenine

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks what replaces uracil in DNA. It is important to first recognize that uracil is a nitrogenous base found in RNA.

2. **Identifying the Nitrogenous Bases**: In nucleic acids, there are four main nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). In RNA, uracil (U) is present instead of thymine.

3. **Recognizing the Role of Thymine**: In DNA, thymine (T) is used in place of uracil (U). This is a key distinction between RNA and DNA.

4. **Explaining the Reason for Replacement**: The replacement of uracil with thymine in DNA serves an important purpose. Thymine is more stable than uracil, which helps in the integrity of the genetic material.

5. **Repair Mechanism**: The presence of thymine instead of uracil aids the DNA repair system. If uracil were present in DNA, it would be difficult for the repair mechanisms to distinguish between uracil that is part of the DNA and uracil that has formed as a result of the deamination of cytosine.

6. **Conclusion**: Therefore, the correct answer to the question is that in DNA, uracil is replaced by thymine.

**Final Answer**: In DNA, uracil is replaced by thymine.

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