Which technique is commonly used to clone DNA?

Polymerase chain reaction (PCR) is a widely used technique for cloning DNA because it allows for the amplification of specific DNA sequences. Through a process that includes repeated cycles of denaturation, annealing, and extension, PCR can generate millions of copies of a particular DNA segment from a small initial sample. This makes it an invaluable tool in molecular biology for cloning purposes, allowing researchers to obtain sufficient quantities of DNA for further analysis, including sequencing or manipulation.

Other techniques mentioned, while relevant in the context of molecular biology, do not serve the primary purpose of cloning DNA in the same direct manner as PCR. Gel electrophoresis is used primarily for separating DNA fragments based on size, Sanger sequencing is a method for determining the sequence of DNA, and restriction enzyme digestion involves cutting DNA at specific sequences but does not amplify DNA. PCR stands out as the technique that specifically addresses the need to clone and amplify DNA efficiently.