One use of the polymerase chain reaction (PCR) is:

• A. Replication of DNA from a crime scene.
• B. Processing RNA transcripts.
• C. Translating proteins.
• D. Assembling ribosomes.

Answer: (A)

PCR amplifies a specific DNA segment, producing many copies of that region in a test tube. This allows investigators to generate enough DNA from small or degraded crime-scene evidence to analyze and compare it with known samples, such as a suspect’s DNA or a database profile. It’s the rapid, targeted copying of DNA that makes forensic analysis feasible when the original sample is scant.

This technique isn’t about processing RNA transcripts, translating proteins, or assembling ribosomes—those involve different cellular processes or other methods. PCR focuses on duplicating DNA, which is why it’s the go-to tool for obtaining trace evidence in forensics.