Chapter 12 Topics Models of Replication Prokaryotic and Eukaryotic Replication Models of Recombination: read pp 339-342

Three Models of DNA Replication Which is correct? http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

DATA TO SUPPORT SEMI-CONSERVATIVE MODEL

Prokaryotic Replication E.coli 4.7 million bp Bacteria can double every 20 minutes at a rate of 1000 nucleotides/second!

2 models of Prokaryotic Replication The Theta Model Rolling Pin Model θ

Theta Replication Radioactive labeled prokaryotic DNA

Rolling Pin Model Occurs in viruses and factor F

Prokaryotic Mechanism of Replication An: overview of E. coli replication

Animation of Elongation http://www.johnkyrk.com/DNAreplication.html Animation of Elongation Nucleotide polymerization http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

Bacterial Mechanism of Replication oriC Key concepts & Proteins Step 1. Initiation Step 2. Unwinding: Helicase helicases

Notice: Directionality Notice: Replication Bubble Forms Helper proteins Helper proteins

Step 3: Primase Step 4. Elongation Okazaki Fragments

Prokaryotes Polymerases The major players are: Pol l Pol II Pol III Pol IV Pol V Removes/replaces primers repair ELONGATION: step 4 repair

Step 5. Ligation These darn Okazaki Fragments! Ligase

Step 6. Termination A certain DNA sequence may replication A protein may physically replication

SUMMARY Prokaryotic DNA replication Leading strand Lagging strand

How are mistakes avoided? By: Nucleotide selection By: Proofreading By: Mismatch Repair

Fidelity of DNA replication Only 1 mistake per billion nucleotides!

Eukaryotic Replication A human chromosome about 100 million bp Replication occurs in minutes to hours!

Answer: Numerous replication origins. Can you notice a difference between this replication process vs bacterial replication? Answer: Numerous replication origins.

Got it!

5’ to 3’ replication occurs in eukaryotes just like in our bacterial friends.

Prokaryotic and Eukaryotic Replication are similar but there are some differences; these include…

Origins “get tagged” by a replication licensing factor.

There are more and different DNA polymerases.

Eukaryotic DNA Polymerases Priming & replication (RNA polymerase Replication Repair & recombination Repair and replication Mitochondrial DNA replication DNA Pol α DNA pol δ DNA pol β DNA pol ε DNA pol γ

Nucleosome Assembly Unique to eukaryotic replication process

What happens when you reach the end of linear DNA?

Oops a problem at the end!!

Are loss of telomeres related to aging? Telomeres and Telomerase! Are loss of telomeres related to aging?

Or is too much telomerase activity related cancer?

Cells with telomerase activity Embryonic cells Intestinal cells And bone marrow

Disease of Aging: Werner’s Disease Related to mutated helicase; Why would this cause an error in DNA replication?

Assignment please read: pp 339-342 The Holliday Model of DNA recombination