DNA Replication: Seeing Double

DNA Replication: Seeing DoubleWeek 8

Rincon High SchoolGo Rangers!

Quote of the Day!

0 “For every fact there is an infinity of hypotheses.” 

0 ~Robert M. Pirsig

Objectives

0The Student will be able to:01.) Describe the process of how DNA replicates itself.02.) Model the process of DNA replication.

Recall

0Where does DNA Replication occur?0Why is DNA replication important?0What can happen if DNA replication goes wrong?

Let’s Make a Model

0At 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).

0Must have a base, ribose and a phosphate group.

If you were in charge….

0How would you start to replication the DNA in front of you?

How it’s really done.

0Step 1 of DNA Replication:

0An enzyme called “Helicase,” comes in and breaks the hydrogen bonds pulling the two DNA strands apart.

0The separated DNA molecule is called a “Replication fork.”

0Create 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

0Another enzyme called “DNA Polymerase I,” attaches itself to one of the separated strands of DNA.

0Once attached DNA Polymerase I starts to copy the DNA strand by attaching the missing parts of the base pair.

0The strand that DNA Polymerase I attaches to is called the “Leading strand.”

What does this look like?

0Model 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

0The other strand is then copied by yet another enzyme called “DNA Polymerase II,” this adds the complimentary base pair.

0The strand that DNA Polymerase II attaches to is called the “Lagging Strand.”

0Create a DNA polymerase II on a piece of paper and model this with your partner.

Step 4 of DNA Replication

0Once DNA Polymerase I and II are finished copying the Leading and Lagging strands two complete strands of DNA separate from one another.

0When 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.

0Create Telomeres out of paper and model this step.

What this step looks like with when finished

Step 5 of DNA Replication

0Enzymes 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.

0What could’ve gone wrong in this process?

Review and Assess

0With your notes and your partner, conduct this entire process of start to finish.