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How do sticky ends help donor DNA join with plasmid DNA?

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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, "sticky ends" are single-stranded nucleotide overhangs created when certain restriction enzymes make staggered cuts in a DNA molecule.1

These overhangs facilitate the joining of donor DNA to plasmid DNA because they are complementary to one another. When both the donor DNA and the vector (plasmid) DNA are cut with the same restriction enzyme, their sticky ends can spontaneously pair together through base-pairing.1

While this pairing allows the two DNA segments to unite, the association is initially unstable because the sugar-phosphate backbone remains unsealed. To create a continuous, stable double helix, an enzyme called DNA ligase is applied to seal the segments together. This precise process is fundamental to genetic engineering, as it allows scientists to reliably insert specific genes into vectors for cloning.123