Final answer:
The restriction enzyme leaves complementary sticky ends on the foreign DNA fragment and the plasmid, allowing for insertion and recombination into the plasmid. DNA ligase is used to reattach the DNA backbones, resulting in recombinant plasmids.
Step-by-step explanation:
The restriction enzyme leaves complementary sticky ends on the foreign DNA fragment and the plasmid. This allows the foreign DNA to be inserted into the plasmid when the sticky ends anneal. Adding DNA ligase reattaches the DNA backbones. These are recombinant plasmids. For a DNA fragment to be inserted, it typically does have two restriction sites on either end; these are recognized by restriction enzymes that cut DNA at these specific sequences, producing either "sticky ends" or "blunt ends.".
In nature, these sites might not be present where needed for cloning purposes, so scientists often add restriction sites to the ends of DNA fragments using techniques like PCR or synthetic means for the desired DNA manipulation. In terms of promoter and terminator regions, they are sometimes naturally present within the fragment, but often they need to be added or assembled in a specific configuration to ensure proper gene expression in recombinant DNA technology. Scientists use ligase to permanently join the annealed sticky ends, creating recombinant plasmids. Plasmids typically have a multiple cloning site (MCS), which contains numerous restriction sites that allow scientists to easily insert genes of interest. Furthermore, engineered plasmids also often contain selectable markers, like antibiotic resistance genes, which facilitate the identification and selection of successfully modified bacteria.