Bacterial plasmids differ from chromosomes in that they are not essential for bacterial growth or metabolism. They are extrachromosomal DNA that can contain genes allowing bacteria to survive in stressful conditions. This document discusses the process of using PCR to isolate the LacZ gene from E. coli and ligate it to a plasmid vector for future experiments. It describes the primer design, PCR reaction setup, and gel electrophoresis to confirm successful amplification of the target gene fragment.