What is the purpose of DNA polymerase in forensic analysis?

• A. It uses RNA as a template to synthesize proteins.
• B. It is used to copy a DNA strand outside of a living cell, known as the polymerase chain reaction (PCR).
• C. It breaks down DNA into nucleotides.
• D. It seals DNA fragments during gel electrophoresis.

Answer: (B)

In forensic analysis, the main idea is that DNA polymerase copies DNA outside a living cell using PCR. This thermostable enzyme builds new DNA strands by extending from primers that flank the target region, adding nucleotides to the growing 3' end. In PCR, cycles of heating and cooling denature DNA, allow primer binding, and then extend the new strand, yielding exponential amplification of specific DNA regions. This amplification is crucial for forensic work because many samples are tiny or degraded, so generating large amounts of DNA makes it possible to perform reliable STR profiling.

The function described here is distinct from other DNA-processing activities. Using RNA as a template to make proteins is done by RNA polymerase and the translation machinery, not DNA polymerase in PCR. Breaking down DNA into nucleotides is done by nucleases, not polymerases. Sealing DNA fragments during gel electrophoresis is not a step in amplification—it’s a mischaracterization of what ligases or other enzymes do in cloning, while gel electrophoresis itself is a separation technique.