Which of the following is not an application of PCR(Polymerase Chain Reaction) ?

The correct answer is Purification of isolated protein.

Step-by-Step Explanation:
Polymerase Chain Reaction (PCR) is a molecular biology technique used to make multiple copies of a specific DNA segment. It is an in vitro method of DNA cloning or amplification. Let's analyze the options to see why "Purification of isolated protein" is not an application of PCR:

1. Gene amplification: This is the primary purpose of PCR. It allows for the exponential amplification of a specific region of DNA from a small template sample. Therefore, this is an application of PCR.
2. Molecular diagnosis: PCR is widely used in diagnostics to detect the presence of pathogens (like viruses or bacteria) by amplifying their DNA/RNA. For example, PCR is used to detect HIV or SARS-CoV-2. Thus, this is an application of PCR.
3. Detection of gene mutation: PCR, followed by sequencing or restriction digestion, is used to identify mutations in specific genes associated with genetic disorders or cancers. Hence, this is an application of PCR.
4. Purification of isolated protein: PCR works exclusively on nucleic acids (DNA and RNA) using DNA polymerases. It does not synthesize, isolate, or purify proteins. Protein purification involves entirely different biochemical techniques such as chromatography (e.g., affinity, ion-exchange, or size-exclusion chromatography) and electrophoresis. Therefore, purification of proteins is not an application of PCR.