The primer molecule required by DNA polymerase is a sho strand of RNA (4-10 bases) complementary to the template strand of the DNA molecule. The primer is synthesized by a specific RNA polymerase known as primase. The growing end of the RNA primer is a free 3'-OH group. The primase does not itself require a primer for initiation of nucleotide synthesis. DNA ligase catalyzes the formation of a phosphodiester bond between the 3'-OH of one fragment of DNA and the 5'-monophosphate group of an adjacent DNA fragment. Polymerase I catalyzes the polymerization of nucleotides and also functions in processing and repair mechanisms. Polymerase III is a pa of a multiprotein complex and is the major replicating enzyme in E. coli.