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

Three Models of DNA Replication Which is correct?

DATA TO SUPPORT SEMI-CONSERVATIVE MODEL

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

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

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 Nucleotide polymerization

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

Notice: Replication Bubble Forms Helper proteins Notice: Directionality

Step 4. Elongation Step 3: Primase Okazaki Fragments

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

Step 5. Ligation Ligase Ligase These darn Okazaki Fragments!

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

Lagging strand Leading strand Prokaryotic DNA replicationSUMMARY

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

Fidelity of DNA replication Only 1 mistake per billion nucleotides! Only 1 mistake per billion nucleotides!

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

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  DNA Pol α  DNA pol δ ß DNA pol β  DNA pol ε  DNA pol γ Priming & replication (RNA polymerase Priming & replication (RNA polymerase Replication Replication Repair & recombination Repair & recombination Repair and replication Repair and replication Mitochondrial DNA replication Mitochondrial DNA replication

Nucleosome Assembly Unique to eukaryotic replication process

What happens when you reach the end of linear DNA?

Oops a problem at the end!!

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

Or is too much telomerase activity related cancer?

Intestinal cells Embryonic cells Cells with telomerase activity 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 The Holliday Model of DNA recombination