A technique for amplifying, or copying, DNA is called

• A. Gel Electrophoresis
• B. Cloning
• C. Polymerase Chain Reaction (PCR)
• D. Sequencing

Answer: (C)

PCR, or Polymerase Chain Reaction, is the method designed to make many copies of a specific DNA segment. It uses a thermostable DNA polymerase, short DNA primers that flank the target region, and cycles of heating and cooling to denature the DNA, allow primers to bind, and extend new DNA strands. Each cycle doubles the amount of target DNA, so after many cycles you get millions of copies from a tiny starting amount. This rapid, targeted amplification is what makes PCR so fundamental for analysis and downstream experiments.

Gel electrophoresis, by contrast, separates DNA fragments based on size after amplification, not how many copies you have. Sequencing determines the exact order of nucleotides in a DNA molecule. Cloning can produce copies of DNA by inserting it into a host cell or plasmid for replication, but it is slower and not the same in vitro amplification process that PCR provides.