Which method rapidly amplifies (copies) a specific DNA sequence in vitro without using bacteria or cloning in cells?

• A. Gel electrophoresis
• B. Sanger DNA sequencing
• C. Polymerase chain reaction (PCR)
• D. Southern blotting

Answer: (C)

Verified step by step guidance

1. Understand the goal: The question asks for a method that rapidly amplifies a specific DNA sequence in vitro, meaning outside of living cells, without using bacteria or cloning techniques.
2. Recall the functions of each method listed: Gel electrophoresis is used to separate DNA fragments by size, not to amplify DNA.
3. Sanger DNA sequencing is a method to determine the nucleotide sequence of DNA, not primarily for amplification.
4. Southern blotting is a technique used to detect specific DNA sequences within a mixture, but it does not amplify DNA.
5. Polymerase chain reaction (PCR) is the method designed to rapidly and specifically amplify DNA sequences in vitro by using cycles of denaturation, annealing of primers, and extension by DNA polymerase.