Download DNA Replication: Seeing Double

Quote of the Day!
0 “For every fact there is an infinity of hypotheses.”
0
~Robert M. Pirsig
Objectives
0 The Student will be able to:
0 1.) Describe the process of how DNA replicates itself.
0 2.) Model the process of DNA replication.
Recall
0 Where does DNA Replication occur?
0 Why is DNA replication important?
0 What can happen if DNA replication goes wrong?
Let’s Make a Model
0 At your table you have many pieces of the DNA
molecule. With a partner construct a DNA molecule
with 4 base pairs (doesn’t matter which ones).
0 Must have a base, ribose and a phosphate group.
If you were in charge….
0 How would you start to replication the DNA in front of
you?
How it’s really done.
0 Step 1 of DNA Replication:
0 An enzyme called “Helicase,” comes in and breaks the
hydrogen bonds pulling the two DNA strands apart.
0 The separated DNA molecule is called a “Replication fork.”
0 Create a “Helicase” on a sheet of paper and show this step
with you desk models.
What does this look like?
Replication Fork
Step 2 of DNA Replication
0 Another enzyme called “DNA Polymerase I,” attaches itself
to one of the separated strands of DNA.
0 Once attached DNA Polymerase I starts to copy the DNA
strand by attaching the missing parts of the base pair.
0 The strand that DNA Polymerase I attaches to is called the
“Leading strand.”
What does this look like?
0 Model this step with your partner, create a DNA
Polymerase I on a separate sheet of paper to use in
this step.
What should this look like?
Step 3 of DNA Replication
0 The other strand is then copied by yet another enzyme
called “DNA Polymerase II,” this adds the complimentary
base pair.
0 The strand that DNA Polymerase II attaches to is called the
“Lagging Strand.”
0 Create a DNA polymerase II on a piece of paper and model
this with your partner.
Step 4 of DNA Replication
0 Once DNA Polymerase I and II are finished copying
the Leading and Lagging strands two complete
strands of DNA separate from one another.
0 When the two DNA molecules separate a molecule
called Telomeres attach to the ends of the DNA and
cap them to ensure the Bases don’t shift around.
0 Create Telomeres out of paper and model this step.
What this step looks like with
when finished
Step 5 of DNA Replication
0 Enzymes called nucleases come in and double check
that the DNA was copied properly.
0 If the nucleases find and error they either fix the
problem directly or have other cell machinery to do so.
0 What could’ve gone wrong in this process?
Review and Assess
0 With your notes and your partner, conduct this entire
process of start to finish.