Dna replication, repair, recombination

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