Chain
Elongation - Synthesis of the new DNA strand takes place by addition of DNA nucleotides to the 3'OH group of the last ribonucleotide of the RNA primer. This synthesis takes place in the 5'-->3' direction and is probably catalysed by DNA polymerase III. The newly synthesized DNA chains have primer RNA attached to their 5' ends.
The RNA primer is hydrolysed by the 5'-->3' exonuclease activity of DNA polymerase I. The resulting gap is filled in by DNA nucleotides, again by the catalytic activity of DNA polymerase I. The newly-made DNA is joined by DNA ligase to form high molecular weight DNA (site A).
