What is the purpose of PCR (polymerase chain reaction)?

• A. To replicate RNA
• B. To amplify DNA segments
• C. To sequence DNA
• D. To repair DNA

Answer: (B)

The primary purpose of polymerase chain reaction (PCR) is to amplify specific segments of DNA. This technique allows for the selective replication of a targeted region of DNA, generating millions of copies from a small initial sample. During PCR, a series of temperature changes facilitate the denaturation of DNA, annealing of primers, and extension by DNA polymerase, resulting in the exponential increase of the desired DNA sequence.

While other options mention related processes, they do not reflect the core function of PCR. Replicating RNA would involve techniques like reverse transcription, sequencing DNA entails determining the nucleotide order of a DNA segment without necessarily amplifying it, and DNA repair refers to the cellular mechanisms that correct damage to DNA structures rather than amplifying them. Therefore, amplifying DNA segments is the distinct and defining purpose of PCR.