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How do plasmids help scientists copy genes and produce proteins in bacteria?

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A step-by-step diagram shows donor DNA and vector DNA cut with restriction enzymes to create overhangs, mixed and sealed with ligase to form recombinant DNA, which is introduced into bacterial cells. The recombinant DNA replicates as the cells divide, producing clones. — biotechnology Steps involved in the engineering of a recombinant DNA molecule.

In biotechnology, plasmids serve as essential vectors for gene cloning and protein production by acting as vehicles that carry foreign DNA into bacterial cells.

To copy genes, scientists use restriction enzymes to cut both the plasmid and the target donor DNA at specific sites, creating complementary single-stranded overhangs. These segments are joined together using DNA ligase, which seals the sugar-phosphate backbone to form a stable recombinant DNA molecule.12

This recombinant plasmid is introduced into bacteria through a process called transformation. Once inside, the plasmid replicates autonomously as the bacteria divide, effectively amplifying the inserted gene into many copies.12

To produce proteins, scientists often use expression vectors, which place the inserted gene adjacent to a bacterial promoter region. This allows the bacterial machinery to transcribe and translate the foreign DNA into functional proteins, such as insulin or growth hormone, turning the bacteria into biological "factories". Plasmids often carry antibiotic resistance genes, which allow researchers to identify and select only those bacteria that have successfully taken up the recombinant plasmid.231