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

Concept: 

• PCR stands for Polymerase Chain Reaction.
• It helps in the amplification of genes (DNA) of interest.

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Explanation

Option 1: 

• PCR can be used to detect mutations in genes in suspected cancer patients too.
• It is a powerful technique to identify many other genetic disorders.
• Therefore, this is the correct application of PCR.

Option 2:  

• Polymerase Chain Reaction (PCR) is a technique that serves the purpose of early diagnosis.
• A low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be detected by amplification of their nucleic acid by PCR.  
• PCR-based assays have been developed that detect the presence of gene sequences of the infectious agents. 
• Therefore, this is the correct application of PCR.

Option 3: 

• The PCR technique is based on the enzymatic replication of DNA.
• In PCR, a short segment of DNA is amplified using primer-mediated enzymes.
• DNA Polymerase synthesizes new strands of DNA complementary to the template DNA.
• Therefore, this is the correct application of PCR.

Option 4:

• Purification of isolated protein cannot be done by PCR.
• The most widely used method for protein purification is affinity chromatography, which separates proteins based on their specific interaction with a matrix.
• Therefore, option 4 is the correct answer.