Which process involves creating many copies of a specific DNA sequence using a DNA polymerase?

• A. Transcription
• B. Translation
• C. Polymerase Chain Reaction (PCR)
• D. Cloning

Answer: (C)

Amplifying a specific DNA sequence with a DNA polymerase is done by Polymerase Chain Reaction. In PCR, short DNA primers bind to the ends of the target region. The reaction goes through cycles of denaturation (separating the strands), annealing (primers attach), and extension (the polymerase builds new DNA starting from the primers). Each cycle doubles the amount of the target sequence, so a tiny starting amount yields many copies. This relies on a heat-stable DNA polymerase, like Taq polymerase, to survive the temperature changes. Transcription makes RNA from DNA, and translation makes protein from RNA, neither of which copies DNA in vitro. Cloning involves inserting DNA into a host organism or vector to replicate, which is a different, more involved process than the rapid in vitro amplification achieved by PCR.