Professor Saltzman continues his presentation on DNA technology by discussing control of gene expression using two methods of RNA silencing: anti-sense therapy and RNA interference. Molecular cloning techniques to mass-produce proteins using plasmid, restriction enzymes, ligase, and antibiotic selection in bacteria are discussed. Steps and molecules involved in polymerase chain reaction are also described. Professor Saltzman explains how to detect mutations in genomic DNA, such as in sickle cell anemia patients, by gel electrophoresis and Southern blotting. Finally, he gives an example of inducing and controlling insulin expression in large animals by cloning into their genome the insulin gene with the lac promoter.