DNA REPLICATION
Pages 200-202
Purpose of DNA Replication
• Why
does DNA replicate?
DNA Replication
•Making a copy of DNA (DNADNA)
•Location: nucleus
•Enzymes used: Helicase and DNA Polymerase
Steps of DNA Replication
1. Helicase unzips and
unwinds the DNA strands
by breaking the hydrogen
bonds, this y-shaped area
is call the replication fork
Steps of DNA Replication
2. DNA Polymerases
add complementary
nucleotides to
exposed strands
Steps of DNA Replication
3. Process continues until
entire strand is copied
•Results in two identical
strands of DNA
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1. First the DNA must unzip:
Enzymes split apart the base pairs
and unwind the DNA.
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2. Bases pair up: Free nucleotides in
the cell find their complementary
bases along the original strand.
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The DNA is now duplicated:
End Result
• Two identical molecules of DNA
• Each DNA molecule has one new and one old
strand
Mechanism of DNA Replication
• DNA replication is
said to be
semiconservative
since each new DNA
molecule made has
one old and one new
strand.
Accuracy and Repair
• Copies must be 100%
accurate WHY?
• Mutation= change in
nucleotide at one
location
• Enzymes proofread and
fix errors