Which of the following techniques serve the purpose of early diagnosis
I. r-DNA technology
II PCR
III ELISA
IV Conventional method of diagnosis (serum, urine analysis,etc)

Answer

To determine which techniques serve the purpose of early diagnosis, we will evaluate each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Techniques**:
- **I. r-DNA Technology**: This involves the manipulation of DNA to create recombinant DNA. While it has applications in diagnostics, it is not primarily used for early diagnosis of diseases.
- **II. PCR (Polymerase Chain Reaction)**: This technique amplifies small amounts of DNA, making it easier to detect pathogens even when they are present in low concentrations. This makes PCR highly effective for early diagnosis.
- **III. ELISA (Enzyme-Linked Immunosorbent Assay)**: This test detects the presence of antibodies or antigens in a sample. While it is useful for diagnosing certain diseases, it may fail to detect low levels of antigens, which can lead to false negatives.
- **IV. Conventional Methods of Diagnosis**: These include serum and urine analysis. They can sometimes miss early-stage infections due to low levels of pathogens, resulting in false negatives.

2. **Evaluating Each Technique**:
- **r-DNA Technology**: Not primarily for early diagnosis.
- **PCR**: Effective for early diagnosis due to its sensitivity.
- **ELISA**: Useful but can miss low-level infections.
- **Conventional Methods**: Often insufficient for early diagnosis due to low sensitivity.

3. **Conclusion**:
- The only technique that consistently serves the purpose of early diagnosis is **II. PCR**.

### Final Answer:
The correct answer is **II. PCR**.

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