Bio3400
Chapter 11
DNA Replication and Recombination
The
of DNA strands allows each strand to serve as a
for synthesis of the
other.
DNA replication in bacteria begins at the
of
replication
and is
.
The DNA helix is
unwound
by proteins called
which bind to the origin of replication and break the
bonds between the bases.
Producing of DNA polymers requires a
primer made by the
enzyme
.
Polymerization is catalyzed by several DNA
polymerases.
Chain
occurs in the 5' to 3' direction by addition of one nucleotide at a time to the 3'
end.
DNA synthesis is continuous along the
strand of the replication
fork,
but is discontinuous along the
strand. Synthesis is
on both
strands.
The RNA primer is removed by
which replaces it with DNA
bases.
The Okazaki fragments are joined together by DNA
, which forms the missing phosphodiester bonds between the fragments.
Prokaryote DNA synthesis
summary.
Eukaryotic DNA synthesis is more complex than that in prokaryotes.
Eukaryotic genomes are
and contain multiple origins of
replication
to allow the genome to be replicated in a few hours.
Several DNA
have been discovered; four partake in replication, the rest are involved in
processes.
Eukaryotic chromosomes are complexed with
,
forming
that also need to be duplicated during DNA synthesis.
Eukaryotic chromosomes are
rather than circular, and pose a problem when terminating
replication
on the
strand.
Repeating sequences of DNA called
are synthesized by the
enzyme
to prevent chromosome shortening in
cells.
Homologous
in general involves DNA
exchange
along two chromosomes with sequence homology.
DNA recombination can also occur by
gene
, caused by excision repair of a heteroduplex in meiosis.