Final answer:
The enzyme DNA ligase is responsible for linking an antibiotic resistance gene with a plasmid vector in the process of molecular cloning, creating recombinant DNA.
Step-by-step explanation:
The linking of an antibiotic resistance gene with the plasmid vector became possible with the enzyme DNA ligase. This enzyme is essential in the process of molecular cloning where it effectively "glues" together the DNA fragments. After a plasmid is cut with a restriction enzyme, creating sticky ends, and the foreign DNA with complementary sticky ends is introduced, the DNA ligase reseals the sugar-phosphate backbone, creating stable and continuous DNA strands. This results in a recombinant plasmid that can be inserted into a bacterial host for replication or protein production.