Which laboratory technique amplifies DNA in vitro using primers, DNA polymerase, and nucleotides?

Which laboratory technique amplifies DNA in vitro using primers, DNA polymerase, and nucleotides?

• A. Clone amplification
• B. Polymerase Chain Reaction (PCR)
• C. DNA Sequencing
• D. Gel Electrophoresis

Answer: (B)

This question probes understanding of a method that rapidly copies a specific DNA segment in a test tube using short primers, a DNA polymerase, and nucleotides. This technique is Polymerase Chain Reaction (PCR). In PCR, the target DNA is subjected to repeated cycles of heating and cooling: denaturation to separate the strands, primer annealing so primers bind to the ends of the region to be copied, and extension where the DNA polymerase builds new strands by adding nucleotides starting from the primers. With each cycle, the amount of target DNA doubles, producing exponential amplification from a tiny starting sample. This distinguishes PCR from DNA sequencing, which determines the sequence of nucleotides rather than amplifying DNA, and from gel electrophoresis, which separates DNA fragments by size rather than generating copies. Cloning-based amplification involves propagation in cells and is not the in vitro, primer-dependent amplification described here.

This question probes understanding of a method that rapidly copies a specific DNA segment in a test tube using short primers, a DNA polymerase, and nucleotides. This technique is Polymerase Chain Reaction (PCR). In PCR, the target DNA is subjected to repeated cycles of heating and cooling: denaturation to separate the strands, primer annealing so primers bind to the ends of the region to be copied, and extension where the DNA polymerase builds new strands by adding nucleotides starting from the primers. With each cycle, the amount of target DNA doubles, producing exponential amplification from a tiny starting sample. This distinguishes PCR from DNA sequencing, which determines the sequence of nucleotides rather than amplifying DNA, and from gel electrophoresis, which separates DNA fragments by size rather than generating copies. Cloning-based amplification involves propagation in cells and is not the in vitro, primer-dependent amplification described here.