1. DNA Transmission 21 Jan, 2005

2. Overview DNA replication is prerequisite to cell division. DNA is replicated by using each strand as template for synthesis of the complementary strand. –one strand is synthesized continuously, the other discontinuously –all nucleotides are added at the 3’ end of the growing strand Replicated chromosomes are partitioned to nuclei of daughter cells in mitosis. Meiosis distributes replicated chromosomes to haploid daughter cells in two nuclear and cell divisions.

3. Overview

4. DNA Replication

5. Okazaki Fragments

6. Polymerization of DNA DNA polymerization requires the following: –dATP, dGTP, dCTP, dTTP (collectively dNTPs) –single-stranded template –primer with free 3’ hydroxyl to accept incoming nucleotide –DNA polymerase, Mg +2 Accessory enzymes –primosome containing RNA primase –helicase to unwind DNA –gyrase to relax supercoils formed by unwinding

7. Priming and Ligation

8. Replication Enzymes

10. Meselson and Stahl

11. Special cases Some circular DNA molecules (e.g., plasmids) replicate by rolling circle model –continuous replication from circular template –discontinuous replication (Okazaki) from displaced single strand Telomeres –specialized ends of linear eukaryotic chromosomes –replicated by telomerase carries small template RNA a type of reverse transcriptase –without telomerase, lagging strands continuously shorten with remover of primer, eventually deleting essential genes

12. Plasmid Replication

13. Telomeres and Telomerase

14. Cell division in eukaryotes Mitosis –an asexual division –equal division of replicated chromosomes –occurs with any number of chromosomes –part of cell cycle Cell cycle –G1: gap (growth) –S: DNA replication, forms sister chromatids –G2: gap (growth) –M: mitosis (nuclear division) and cytokinesis

17. Meiosis and Fertilization

24. Assignment: Concept map, solved problems 1 and 2, basic problems 7, 10, 13, 15, challenging problems 23, 24, 27 Web-based NCBI tutorial sections from Introduction to Using BLAST to compare sequences. Should now be finished with BLAST tutorial.