Replisome, PCR, and DNA Repair C483 Spring 2013

1. Which proteins are responsible for the unwinding of the double-stranded DNA during replication? A) Ligases. B) Helicases. C) Topoisomerases. D) Primases. E) Lyases. 2. Put these events of PCR in the right order: A) Primers anneal to single stranded DNA B) Heating denatures DNA C) Polymerase replicates DNA sequence 3. Deaminated bases must be removed from DNA because A) they distort the molecule. B) they form thymine dimers. C) they pair incorrectly during replication. D) the mRNA formed may be irregular.

Model of the Replisome Key question: How can simultaneous, one directional DNA replication happen when strands have to be synthesized in opposite directions?

Basic Model

Single Strand Binding Proteins

Helicase and Primase

Polymerase Chain Reaction DNA amplification Thermocycler Primer Taq polymerase annealing

DNA Sequencing Sequencing of base pairs in gene or organism Genomics and shotgun methods Traditional: Sanger method dideoxynucleotides

DNA Repair: Excision Damage from loss of base, deamination, alkylation Recognition of distorted helix Helicase, endonuclease, polymerase, ligase

Common: Deamination of C Hydrolytic deamination of cytidine common Leads to uridine Why does it make sense that thymidine is found in DNA?

Answers 1.B 2.B  A  C 3.C