DNA synthesis on the leading & lagging strands of a DNA molecule
Synthesis
occurs by extension of a 5'
3'
RNA Primer (blue). On the leading strand,
the 5'
3'
direction is directed towards the replication fork: a
single primer can be extended indefinitely as the fork
opens. On the lagging strand, the 5'3'
direction is directed away from the fork: synthesis must
be re-primed periodically as more template is exposed.
This produces a discontinuous set of molecules called Okazaki
Fragments.
3'
RNA Primer (blue). On the leading strand,
the 5'3'
direction is directed towards the replication fork: a
single primer can be extended indefinitely as the fork
opens. On the lagging strand, the 5'3'
direction is directed away from the fork: synthesis must
be re-primed periodically as more template is exposed.
This produces a discontinuous set of molecules called Okazaki
Fragments.Figure © 2012 TA Brown, Introduction
to Genetics (1st ed.); additional
text © 2014 by Steven M. Carr