PCR-technique is used in

Options

A. Production of transgenic microbe
B. Production of genetically modified food
C. Forensic investigation
D. r-DNA technology

Answer

### Step-by-Step Solution:

1. **Understanding PCR**: The first step is to understand what PCR stands for. PCR stands for Polymerase Chain Reaction. It is a technique used to amplify small segments of DNA, making millions of copies of a specific DNA sequence.

2. **Applications of PCR**: Next, we need to look at the various applications of PCR. The question lists four options:
- Production of transgenic microbes
- Production of genetically modified food
- Forensic investigation
- Recombinant DNA technology

3. **Analyzing Each Option**:
- **Production of Transgenic Microbes**: This typically involves recombinant DNA technology, where DNA from one organism is inserted into another organism's genome. PCR is not directly used for the production of transgenic microbes.
- **Production of Genetically Modified Food**: Similar to transgenic microbes, this process also relies on recombinant DNA technology and not specifically on PCR.
- **Forensic Investigation**: PCR is widely used in forensic science to amplify DNA from crime scenes, allowing for DNA profiling and fingerprinting. This is a key application of PCR.
- **Recombinant DNA Technology**: While PCR can be used in the process of creating recombinant DNA, it is not the primary technique for producing recombinant DNA itself.

4. **Conclusion**: Based on the analysis, the most appropriate application of PCR from the given options is **forensic investigation**. This is because PCR allows for the amplification of DNA samples collected from crime scenes, which can then be analyzed for identification purposes.

### Final Answer:
The PCR technique is primarily used in **forensic investigation**.

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