RNA Primer

RNA Primer

	RNA Primer Initiation of DNA synthesis requires an RNA primer. DNA polymerases cannot initiate DNA chains de novo.(RNA polymerases, in contrast, can initiate chains de novo during transcription) .A pre existing polynucleotide chain (the primer) is required to which polynucleotides are added.
The primer RNA is a short poly nucleotide chain with a 5' triphosphate end and a 3'-OH end. The RNA primer is synthesized by the DNA template close to the origin of replication. This synthesis is probably catalysed by a modified RNA polymerase which may contain a starting factor. In E. coli RNA polymerase is required just before replication of DNA, but protein synthesis is not.
In other words there is transcription but not translation during RNA primer formation. In E. coli, although RNA may serve as a primer for the synthesis of DNA chains, it need not necessarily be transcribed on DNA by RNA polymerase. A preformed RNA molecule can also serve primer function. For example, a tRNA molecule is utilized by the reverse transcriptase of oncornaviruses.

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Polymerase II - Pol II Polymerase III - Pol III Characteristics of DNA Polymerases Eukaryotic DNA Polymerases Models of Replication Cairns Model of Replication Yoshikawa Model of Replication Rolling Circle Model of Replication Replication in Duplex Rod Prokaryote Chromosome Replication in Eukaryote Chromosome Repair Replication Functions of DNA