Fig. 9: DNA Replication by Complementary
Base Pairing: Adding DNA Nucleotides to the RNA Primer
DNA polymerase III replaces the
primase and is able to add DNA nucleotides to the RNA primer. As the free deoxyribonucleoside
triphosphates line up by complementary base pairing with the nucleotides on each
parent strand of the unwound DNA in the replication fork, the phosphate on the
5' carbon of the newest building block lining up then forms a phosphodiester bond
with the 3' carbon of the last nucleotide in the growing strand. During the process,
two phosphates are lost . Because the parent strands are antiparallel and DNA
can only be replicated in a 5' to 3' direction, the the two new strands must be
synthesized in opposite directions.
