Cell & Molecular Biology
Dna replication, repair, recombination
May 24, 2015
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Cell & Molecular
Biology
DNA Replication,Repair andRecombination
Chapter 6
DNA Replication
Three models of DNA replication
Figure 6-6 Essential Cell Biology (© Garland Science 2010)
Each strand of DNAin a double helixserves as a template
Base Pairingis at the heartof DNA replication
Figure 6-4 Essential Cell Biology (© Garland Science 2010)
Replication Origins
“...positions at which the DNAis first opened up... usually marked by a particular sequence of nucleotides.”
Figure 6-5 Essential Cell Biology (© Garland Science 2010)
Replication Forks
Figure 6-9 Essential Cell Biology (© Garland Science 2010)
DNA replicationis bidirectional
DNA is synthesized5’ to 3’
Figure 6-10 Essential Cell Biology (© Garland Science 2010)
Figure 6-11 Essential Cell Biology (© Garland Science 2010)
Leading and lagging strands
Figure 6-12 Essential Cell Biology (© Garland Science 2010)
DNA Polymerase
Accuracy
Nucleotide addition is catalyzed only when base-pairing is correct.
Figure 6-13 Essential Cell Biology (© Garland Science 2010)
Proofreading clips out added nucleotides thatdo not correctly base-pair.
Figure 6-14 Essential Cell Biology (© Garland Science 2010)
For proofreading to work,DNA must be synthesizedfrom 5’ to 3’.
Figure 6-15 Essential Cell Biology (© Garland Science 2010)
DNA polymerase can only add nucleotides to a base-paired nucleotidein a DNA double helix.
So the synthesis of DNAbegins with RNA primers.
Figure 6-17a Essential Cell Biology (© Garland Science 2010)
Figure 6-16 Essential Cell Biology (© Garland Science 2010)
Figure 6-17a Essential Cell Biology (© Garland Science 2010)
Figure 6-17b Essential Cell Biology (© Garland Science 2010)
The Replication Machine
Helicase
Single-Strand Binding Protein
Sliding Clamp
Clamp Loader
DNA Primase
Telomerase
Figure 6-17b Essential Cell Biology (© Garland Science 2010)
Figure 6-18 Essential Cell Biology (© Garland Science 2010)
DNA Repair
Replication Errors
Figure 6-21a Essential Cell Biology (© Garland Science 2010)
Figure 6-21b Essential Cell Biology (© Garland Science 2010)
Figure 6-21c Essential Cell Biology (© Garland Science 2010)
Mismatch Repair
Figure 6-22 Essential Cell Biology (© Garland Science 2010)
DNA Damage
Depurination
Deamination
Figure 6-23 Essential Cell Biology (© Garland Science 2010)
Figure 6-25a Essential Cell Biology (© Garland Science 2010)
Figure 6-25b Essential Cell Biology (© Garland Science 2010)
ThymineDimerization
Figure 6-24 Essential Cell Biology (© Garland Science 2010)
Repair: 1. excision2. resynthesis3. ligation
Figure 6-26 Essential Cell Biology (© Garland Science 2010)
Double-Stranded Breaks
Nonhomologous End-Joining
Figure 6-27 Essential Cell Biology (© Garland Science 2010)
HomologousRecombination
“...the exchange of genetic information between a pair of homologous DNA molecules...”
Double-strandedbreak repair
Figure 6-31 (part 1 of 2) Essential Cell Biology (© Garland Science 2010)
Figure 6-31 (part 2 of 2) Essential Cell Biology (© Garland Science 2010)
Meiosis
Page 183
Figure 6-30 Essential Cell Biology (© Garland Science 2010)
Figure 6-31 (part 1 of 2) Essential Cell Biology (© Garland Science 2010)
Figure 6-31 (part 2 of 2) Essential Cell Biology (© Garland Science 2010)
Mobile GeneticElements
or,Transposons
DNA-Only Transposons
Figure 6-32 Essential Cell Biology (© Garland Science 2010)
3 Bacterial Transposons
Transposase
Figure 6-33 Essential Cell Biology (© Garland Science 2010)
Retrotransposons
Figure 6-34 Essential Cell Biology (© Garland Science 2010)
Reverse Transcriptase
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