DNA as an acidic substance present in nucleus was first identified by

Options

A. Watson
B. Griffith
C. Levene
D. Friedrich Meischer

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks who first identified DNA as an acidic substance present in the nucleus.

2. **Historical Context**: To answer this, we need to look back at the history of DNA discovery. The identification of DNA occurred in the 19th century.

3. **Identifying the Researcher**: The researcher who first identified DNA was Johan Friedrich Miescher. He conducted his research in 1869.

4. **Research Focus**: Miescher was studying lymphoid cells, which are a type of white blood cell. During his studies, he observed the nucleus of these cells.

5. **Significance of Discovery**: Miescher discovered a substance that was acidic and rich in phosphorus, which he named "nuclein." This substance was later understood to be DNA.

6. **Elimination of Other Options**:
- Option A (Watson) refers to Watson and Crick, who are known for describing the double helix structure of DNA in 1953, not for its initial identification.
- Option B (Griffith) refers to the transformation experiment in bacteria in 1928, which demonstrated that DNA is the genetic material but did not identify DNA itself.
- Option C (Lavin) contributed to the understanding of sugars in nucleic acids but did not identify DNA.

7. **Conclusion**: Therefore, the correct answer to the question is Johan Friedrich Miescher, who first identified DNA as an acidic substance present in the nucleus in 1869.

**Final Answer**: Johan Friedrich Miescher

---