and (Restriction Endonuclease): To create a functional recombinant DNA molecule, both the source (foreign) DNA and the vector (plasmid) DNA must be cleaved at specific palindromic sequences. This cutting is performed by the exact same restriction endonuclease (such as EcoRI) to ensure they produce perfectly matching, complementary single-stranded overhanging "sticky ends".

(DNA Ligase): Once the complementary sticky ends of the foreign DNA fragment and the cut vector DNA align through hydrogen bonding, DNA ligase acts as molecular glue. It covalently links the fragments by sealing the sugar-phosphate backbone, completing the chimeric recombinant DNA molecule.

(Transformation): The newly constructed recombinant DNA molecule must be introduced into a living recipient bacterial host cell (like E. coli). The biological uptake mechanism of naked foreign plasmid DNA by a competent host cell is formally referred to as transformation.

──────────────────────────────────────────────────────────────────────────────────────────