MCQ – 100164

Correct Answer � A Explanation

Polymerase Chain Reaction (PCR) is a revolutionary molecular biology technique developed by Kary Mullis, which allows rapid amplification of a specific segment of DNA. It can generate millions of copies of a target DNA sequence from a minimal initial sample.

Applications of PCR:

• Genetic testing (e.g., for mutations, inherited diseases)

• Pathogen detection (e.g., viruses like HIV, SARS-CoV-2)

• Forensic analysis (DNA fingerprinting)

• Paternity testing

• Molecular cloning

PCR (Basic Steps):

1. Denaturation – Heating separates the double-stranded DNA.

2. Annealing – Primers bind to the specific target sequence.

3. Extension – DNA polymerase synthesizes the new strand using dNTPs.

Each cycle doubles the amount of DNA, resulting in exponential amplification.

Why the Other Options Are Incorrect:

B. DNA sequencing 

• PCR is often a preparatory step before sequencing, but not sequencing itself.

• DNA sequencing is performed by Sanger, Next-Gen, or Nanopore methods.

C. Screening gene libraries 

• Requires hybridization or vector-based screening.

• PCR can be used to probe libraries, but it’s not the main purpose.

D. Synthesis of polymerases 

• Polymerases are enzymes used in PCR, not synthesized by it.