DNA Replication
Watch this video to see how
DNA replication actually occurs.
• http://www.youtube.com/wat
ch?v=hfZ8o9D1tus
DNA Replication
• During DNA replication, the DNA molecule
(double helix) separates into two strands. Next,
two new complementary strands are produced
by following the rules of base-pairing.
• Base-pairing – principle that bonds in DNA
can form only between adenine and thymine
and between guanine and cytosine
A --- T
G --- C
DNA Replication
• DNA replication is carried out by a
series of enzymes. These
enzymes “unzip” the double-helix
by breaking the hydrogen bonds
that exists between the base pairs.
Once the original strands are
unwound, each strand serves as a
template for the attachment of
complementary bases.
DNA Replication
• The enzyme, DNA polymerase, is the principal enzyme
involved in DNA replication. DNA polymerase
polymerizes (“reads” and attaches) individual nucleotides
to the template DNA strand. DNA polymerase also
“proofreads” each new DNA strand, ensuring that the
correct nucleotides were attached.
DNA Replication
• In most prokaryotes, DNA replication begins at a single
location. Alternatively, eukaryotic chromosomes
replicate in multiple locations simultaneously. In both
cases, replication proceeds in both directions until the
chromosome is completely copied. The sites where
separation and replication occur are called replication
forks.
DNA Replication
electron
micrograph
images of real
chromosomes
undergoing
replication