11.24.09
DNA Replication Process
When DNA replicates, its strands are separated by the enzyme helicase.
Single stranded DNA binding proteins keep the strands from reannealing. One DNA strand encodes the leading strand which forms from its 5’ to its 3’ end using DNA Polymerase III. No problem here (pointing to continuous replication of leading strand), but the lagging strand presents problems. It has to form from 5’ to 3’ too. It forms in pieces called Okazaki fragments.
· First, a RNA primase lays down a RNA primer.
· Then, DNA polymerase III lays down new DNA. The process repeats again and again.
· DNA polymerase I replaces the RNA primers with DNA.
· Finally, DNA ligase links the Okazaki fragments.
