Paper 2 · genetic engineering / recombinant DNA technology
In genetic engineering, a plasmid and a human gene are cut with the same restriction enzyme so that their cut ends are complementary. Which enzyme is then used to join (splice) the human gene into the cut plasmid to form a recombinant plasmid?
Model answer
DNA ligase
Also accepted: ligase
Explanation: After the plasmid and the human gene are cut with the same restriction enzyme, their matching sticky ends can base-pair with each other. DNA ligase then catalyses the formation of phosphodiester bonds in the sugar-phosphate backbone at these joins, sealing the human gene into the plasmid to form a single recombinant molecule.
Derived from ZIMSEC Biology Paper 2, November 2008, Q1 (Topic 5 Genetic Engineering)
