1. Do Now
What is replication?
Where does this take place?

2. DNA Replication!

3. Objectives
Explain what replication is and why it must occur in our bodies.
List the different enzymes involved in each step of replication and what they do.
Compare and contrast leading vs. lagging strands.

5. Semiconservative Replication
Parental strands of DNA separate
Each strand serve as template
DNA molecules produced have one strand of parental DNA (old) and one daughter strand (new)

6. Enzymes involved Helicase- Unzips the DNA strand.
Primase- RNA Primer (tells the next enzyme where to begin!)
DNA polymerase- adds nucleotides.
DNA ligase- links together fragments.

7. Steps to DNA Replication 1. Unwinding
DNA helicase (enzyme) unwinds and unzips the DNA – breaking the hydrogen bonds between the strands
Single-stranded binding proteins- go to DNA strand to keep them separated during replication.
RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand.

8. Steps to DNA replication
DNA unwinds at different spots (Origins)
At the replication fork, an enzyme (Helicase) breaks the hydrogen bonds between the bases.

9. Steps to DNA Replication 2. Base Pairing
DNA polymerase (enzyme) adds complementary nucleotides to parent DNA strand
Only adds in the 5’ to 3’ direction.

10. 2. Base Pairing (cont.)
Two daughter strands of DNA are made differently
Leading Strand- Elongated as the DNA unwinds.
Built continuously with out breaks
Lagging Strand- Elongates away from replication fork.
Built discontinuously
makes several small fragments of DNA called Okazaki Fragments

11. Leading and Lagging Strands

12. Steps to DNA Replication 3. Joining
DNA Polymerase removes RNA Primer and fills it in place with DNA nucleotides
DNA ligase links the Okazaki Fragments.

13. DNA Replication

14. Mistakes in DNA DNA replication takes a lot of energy.
During replication, mistakes are made. (mutations)
Enzymes “proof read” and repair the mistakes.

15. Eukaryotes VS. Prokaryotes
Eukaryotic DNA unwinds in multiple areas as DNA is replicated.
In prokaryotes, the circular DNA strand is opened at one origin of replication.

16. Do Now Label the diagram

17. Review What are the steps of replication?
(Include the enzymes involved in your explanation)
What would happen if helicase wasn’t available?
Ligase?
RNA Primase?
Contrast the leading and lagging strands.

18. Do Now
Label the DNA Replication Diagram

19. http://highered. mheducation
udent_view0/chapter3/animation__dna_replication__ quiz_1_.html