1. DNA Replication - copying DNA molecule

2. Why does DNA need to copy? Every time a cell divides (mitosis), an EXACT copy of DNA must go into new cells! Growth and repair of body cells

3. Origins of replication Prokaryotes – one origin in two directions along the plasmid

4. Eukaryotes – many origins, or forks, along DNA strand

5. Replication is Semiconservative One old and one new

6. Step One: Enzyme Helicase breaks hydrogen bonds between base pairs (unwinds at rate of 8,000 rpm) DNA unzips at Replication Fork

7. Step Two RNA primer Template to begin replication

8. Step Three: Free floating nucleotides pair up with lone nucleotides in a 5’-3’ direction

9. Step Four: Base pairs bonded together by enzyme called DNA POLYMERASE

10. Step Five: Side of ladder is bonded by enzyme called LIGASE

12. How do new strands grow?

13. Leading Strand Replicated continuously 5’ to 3’ end

14. Lagging Strand Replicated in short fragments called “Okazaki fragments” (1,000-2,000 bp long) 5’ to 3’ end

15. The two new strands are identical to eachother and the original parent molecule!

16. Proofreading DNA polymerase detects, removes and replaces incorrectly paired nucleotides. If not corrected, could lead to mutations, loss of functions etc.

17. Damage Repair Corrects damage caused by X-rays, UV radiation, chemical exposure etc. One 4 hour day at the beach – approx. 10 UV induced errors in every skin cell