1. Replication pp. 200-202

2. Quick Review (don’t need to write this)  What is DNA made of?  What type of bond holds a nucleotide together?  What type of bond holds the bases together?

3. Replication  Making copies of DNA  Occurs when a cell divides to make new cells  The two strands “unzip” to act as a template for making new nucleotides

5. Step 1:  Helicase breaks the hydrogen bonds between the bases  Replication Fork : the point where DNA is separated

6. Step 2:  DNA Polymerase follows the helicase, matching new nucleotides to old ones  New nucleotides were floating freely inside the nucleus

7. Step 2 (continued):  Continues until the entire strand is copied  Results in two strands of DNA  Each strand is semi-conservative (50% old DNA, 50% new DNA)

8. Errors in DNA  Copies must be 100% accurate  Enzymes proofread & fix errors  If an error isn’t fixed, it causes a mutation  Mutation : change in nucleotide at one location FUN FACT: chance of an error occurring: one in one billion.

9. Vocabulary  Helicase  Replication Fork  DNA Polymerase  Mutation  Turn to the person across from you and discuss: - One step of Replication - Causes of Mutations