1. Fig. 16-17 Overview Origin of replication Leading strand Lagging strand Overall directions of replication Leading strand Lagging strand Helicase Parental DNA DNA pol III PrimerPrimase DNA ligase DNA pol III DNA pol I Single-strand binding protein 5 3 5 5 5 5 3 3 3 3 1 3 2 4

2. Figure 16.18 Parental DNA DNA pol III Leading strand Connecting protein Helicase Lagging strand DNA pol III Lagging strand template 5 5 5 5 5 5 3 3 3 3 3 3

3. Cool animation of DNA replication (and other stuff) http://www.ted.com/talks/drew_berry_animations_of_unseeable_biology.html

4. How do we know all this? -That the lagging strand is made in fragments -That DNA ligase joins these fragments together

5. Mixture of DNA mol- ecules of different sizes Power source Longer molecules Cathode Anode Wells Gel Shorter molecules TECHNIQUE 2     1 Gel electrophoresis

6. DNA Pol III Where do mutations come from?

7. E.Coli genome: 4.6 x 10^6 b.p. H. Sapiens genome (diploid): 6 x 10^9 b.p. ~1 “error” for every 10 10 bases replicated DNA pol III adds the wrong base every 10 5 bases How often do mutations occur? Extra fidelity comes from: 1. “Proofreading” by DNA pol III (and pol I) 2. Mismatch repair pathway

8. E.Coli genome: 4.6 x 10^6 b.p. H. Sapiens genome (diploid): 6 x 10^9 b.p. ~1 “error” for every 10 10 bases replicated DNA pol III adds the wrong base every 10 5 bases How often do mutations occur?

9. E.Coli genome: 4.6 x 10^6 b.p. H. Sapiens genome (diploid): 6 x 10^9 b.p. ~1 “error” for every 10 10 bases replicated DNA pol III adds the wrong base every 10 5 bases How often do mutations occur? Extra fidelity comes from: 1. “Proofreading” by DNA pol III (and pol I) 2. Mismatch repair pathway Chemically damaged DNA can lead to much higher rates of mutation

10. Fig. 16-18 Nuclease DNA polymerase DNA ligase Example of damaged DNA: thymine dimer caused by UV radiation Nucleotide Excision Repair pathway has removed and replaced damaged bases

12. Fig. 16-18 Nuclease DNA polymerase DNA ligase Nucleotide Excision Repair pathway removes and replaces damaged bases Example of damaged DNA: thymine dimer caused by UV radiation

13. Fig. 16-12b 0.25 µm Origin of replicationDouble-stranded DNA molecule Parental (template) strand Daughter (new) strand Bubble Replication fork Two daughter DNA molecules (b) Origins of replication in eukaryotes Eukaryotic replication

14. Fig. 16-19 Ends of parental DNA strands Leading strand Lagging strand Last fragment Previous fragment Parental strand RNA primer Removal of primers and replacement with DNA where a 3 end is available Second round of replication New leading strand New lagging strand Further rounds of replication Shorter and shorter daughter molecules 5 3 3 3 3 3 5 5 5 5

15. Fig. 16-19 Ends of parental DNA strands Leading strand Lagging strand Last fragment Previous fragment Parental strand RNA primer Removal of primers and replacement with DNA where a 3 end is available Second round of replication New leading strand New lagging strand Further rounds of replication Shorter and shorter daughter molecules 5 3 3 3 3 3 5 5 5 5

16. Fig. 16-20 1 µm Staining of telomeres Florescence In Situ Hybridization (FISH) “probe” = (5’-CTAACC-3’) 100

17. 08_Figure37.jpg

18. Fig. 16-7a Hydrogen bond 3 end 5 end 3.4 nm 0.34 nm 3 end 5 end (b) Partial chemical structure(a) Key features of DNA structure 1 nm

19. Fig. 16-21a DNA double helix (2 nm in diameter) Nucleosome (10 nm in diameter) Histones Histone tail H1 DNA, the double helixHistones Nucleosomes, or “beads on a string” (10-nm fiber)

20. Fig. 16-21b 30-nm fiber Chromatid (700 nm) LoopsScaffold 300-nm fiber Replicated chromosome (1,400 nm) 30-nm fiber Looped domains (300-nm fiber) Metaphase chromosome