Lecture 15: DNA Organization, Replication and Repair Reading Assignment: Chapter 38, pgs ; Harper’s Biochemistry (25 th edition). Objective: To understand the structures and proteins involved in DNA replication. I. Cellular DNA exists as chromatin A. Nucleosomes 1. Histones II. General characteristics of DNA replication A. Semi-conservative B. Starts at specific sites C. Bidirectional III. General characteristics of DNA polymerases A. Use DNA as a template B. Replicate DNA with high fidelity C. Catalyze the formation of phosphodiester bridge IV. Characteristics and function of procaryotic DNA polymerases V. Characteristics and function of eucaryotic DNA polymerases

VI. Characteristics and function of other proteins involved in DNA replication VII. Steps in DNA replication VIII. DNA replication at chromosome ends A. General structure of chromosome ends B. Enzyme involved in replication of chromosome ends IX. Types of DNA mutations A. Single base alterations 1. Transitions 2. Transversions B. Two base alterations 1. Pyrimidine dimers C. Chain breaks D. Cross links X. Types of DNA repair systems A. Direct repair B. Excision repair C. Mismatch repair