Which method can be used to amplify DNA in vitro?

The ability to amplify DNA in vitro is crucial for a variety of molecular biology applications, including cloning, sequencing, and analysis of genetic material. The method that is primarily used for this purpose is polymerase chain reaction (PCR).

PCR works by utilizing specific primers that bind to the target DNA sequence, followed by repeated cycles of heating and cooling that allow for the denaturation of DNA, annealing of primers, and extension by a DNA polymerase enzyme. This results in exponential amplification of the intended DNA segment, often producing millions of copies from a small initial amount of DNA.

Other methods listed serve different purposes:

• Western blotting is a technique used for protein detection and analysis, not DNA amplification.

• ELISA (Enzyme-Linked Immunosorbent Assay) is used for detecting and quantifying proteins or hormones through antigen-antibody interactions, again not applicable for DNA amplification.

• Sequencing refers to determining the precise order of nucleotides in a DNA molecule but does not amplify DNA.

Thus, PCR stands out as the only technique among the options provided that specifically and effectively amplifies DNA in vitro.