1. Chapter 16 DNA REPLICATION

2. REVIEW: HISTORY & STRUCTURE

3. GRIFFITH’S EXPERIMENT

4. HERSHEY & CHASE’S EXPERIMENT

5. AVERY, M C CARTY, & MACLOED’S EXPERIMENT

6. WILKINS & FRANKLIN’S EXPERIMENT

7. CHARGAFF’S EXPERIMENT

8. WATSON & CRICK

9.  Making DNA from existing DNA  Semi- conservative  At the end of DNA replication, each daughter molecule has one old strand (from the parent DNA) and one new strand (synthesized during replication) DNA REPLICATION

10.  Step 1:  Helicases unwind DNA at origin of replication by breaking hydrogen bonds between nitrogen bases  Replication bubble forms as two parental strands separate  Replication fork forms at end of each replication bubble DNA REPLICATION

11.  Step 2:  Single-strand binding proteins hold the unpaired DNA strands apart while new DNA strands are being synthesized  Topoisomerase protein binds to parental DNA to relieve strain untwisting puts on replication fork DNA REPLICATION

12.  Step 3:  Primase creates a short RNA primer that binds to the parent DNA to signal DNA polymerase III where to begin adding nucleotides  RNA primer will later be replaced with DNA nucleotides DNA REPLICATION

13.  Step 4:  DNA Polymerase III adds nucleotides to exposed bases in 5’-3’ direction at the RNA primer  Leading strand  Produced continuously in 5’-3’ direction  Elongation moves towards replication fork  Lagging strand  Produced in pieces  Okazaki fragments  Elongation moves in opposite direction of replication fork (5’-3’)

14.  Step 5:  Lagging strand is completed as DNA ligase seals Okazaki fragments

16.  Initial error rate in replication is 1 in 100,000 nucleotides  DNA polymerases proofread and correct errors  Error rate in completed replication is 1 in 10 billion bases PROOFREADING & REPAIR

17.  For that 1 in 10 billion errors that escapes DNA polymerase or are due to environmental mutations  Many enzymes involved  Cut out damaged section (nuclease)  Replace with new nucleotides (DNA polymerase)  Seal in place (DNA ligase) MISMATCH REPAIR

18.  As cells divide, chromosomes erode after multiple DNA replications  Telomeres  End caps of non-coding DNA that protect the coding genes on the chromosomes  Think of the plastic pieces on the ends of your shoelaces  These sequences shorten after each round of replication so the actual genes do not  Part of aging process? TELOMERES

19.  Enzyme that lengthens the ends of telomeres in germ cells (give rise to gametes)  Prevents loss of critical genes in zygote  Cancer cells have mechanisms that activate telomerase to allow unlimited division without loss of DNA TELOMERASE

20.  Bioflix animation Bioflix animation  DNA replication cartoon DNA replication cartoon ANIMATIONS

21. EXTENSIVE REPLICATION  http://www.wiley.com/college/pratt/0471393878/student/an imations/dna_replication/index.html http://www.wiley.com/college/pratt/0471393878/student/an imations/dna_replication/index.html

22. CHROMOSOME ANYONE?  http://www.biostudio.com/d_%20Replication%20of%20a%20 Chromosome.htm http://www.biostudio.com/d_%20Replication%20of%20a%20 Chromosome.htm