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Why must donor DNA and vector DNA often be cut with the same restriction enzyme?

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DNA extraction and recombinant DNA technology — recombinant DNA The process of DNA extraction is necessary to isolate molecules of DNA from cells or tissues. A series of steps, including the use of protease enzymes to strip proteins from the DNA, are required for isolating pure DNA that is suitable for use in later procedures, such as cloning or sequencing.

In recombinant DNA technology, donor DNA and vector DNA are often cut with the same restriction enzyme to ensure they can successfully join together.1

Many useful restriction enzymes create staggered cuts, which leave behind single-stranded nucleotide overhangs at the cleavage site. Because these overhangs are complementary, they act like "molecular glue" that allows the donor DNA fragment to pair specifically with the cut vector. By using the same enzyme for both, researchers ensure that the ends of the donor fragment and the vector are compatible, significantly increasing the likelihood that they will splice together to form a stable recombinant DNA molecule. Once these complementary ends unite, an enzyme called DNA ligase is used to seal the sugar-phosphate backbone, creating a continuous and stable double helix.1