prokaryotic dna organization
TRANSCRIPT
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Fig. 11.8
Prokaryotic DNA organization
• Circular DNA• Condensed by
packaging proteins(e.g. H-NS, IHF)
• Supercoiled
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Bidirectionalreplication
• Replication starts atori (oriC in E. coli)
• Continuesbidirectionally
• Chromosome attachedto plasma membrane
Fig. 11.11
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Rolling circle replication
Fig. 11.12
Used by plasmids and somebacteriophage
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DNApolymerases
• 3 DNA polymerases• Synthesize 5´-3´• DNA pol III = DNA
replication• DNA pol I, II = DNA
damage repair
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Replication fork
Fig. 11.15
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Quinolones
Fig. 35.5
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Fig. 35.6
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DNA replication
Fig, 11.16
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Fig. 11.16
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DNA ligase
• Can ligate 5´-PO4 to 3´OH without insertionof nucleotide
Fig. 11.17
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Creating arecombinantplasmid
Fig. 14.4
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Steps in cloning a gene
• Isolate plasmid vector– Plasmid DNA isolation
• Isolate gene of interest– Chromosomal DNA isolation– Polymerase chain reaction
• Cut plasmid and gene of interest with samerestriction endonuclease
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Polymerase chainreaction (PCR)
• Requires DNApolymerase that is notinactivated by hightemperatures
• Taq, Ventpolymerases isolatedfrom thermophiles
Fig,14.8
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Restriction endonucleases
Fig. 14.2
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Fig. 14.11
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Fig. 14.11
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Transcription of RNA
Fig. 11.21
mRNA
rRNA
tRNA
sRNA
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Fig. 11.22
Prokaryotic Promoter
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Fig. 12.2
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Prokaryotic Terminator
Fig. 12.3
• Rho-independent=– 6 uridines follow hairpin– Requires no accessory
proteins• Rho-dependent=
– No uridines after harpin– Requires Rho to displace
RNA polymerse
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Rifampin
• Binds to RNA polymerase• Inhibits transcription, killing cell
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Polycistronic mRNA
Fig. 12.1
• Multiple genes on single transcript• Transcription from a single promoter• Usually genes on a polycistronic mRNA are related to a
specific function or structure• No introns in within genes
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Coupled transcription-translation
Fig. 12.6
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Prokaryotic Ribosome
Fig. 12.12
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Fig. 12.12
Translational Domain• Formed by association of 30S and 50S subunits• 16S rRNA binds to and aligns mRNA
16S rRNA 3´-UUCCUU-5´mRNA 5´-AAGGAA-3´
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tRNA structure
Fig. 12.7
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Amino-acyl tRNA=“Charged” tRNA-cognate amino acid attachedto 3´ end
Fig. 12.10
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Initiation ofProtein
Synthesis
Fig. 12.14
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Fig. 11.19
Alignment to allow in-frame translation
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Initiation ofProtein
Synthesis
Fig. 12.14
tRNA 3´-UAC-5´mRNA 5´-AUG-3´
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Prokaryotic Initiator tRNA
Fig. 12.13
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Elongation
Fig. 12.15
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Peptide Bond Formation
Fig. 12.16
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Termination
Fig. 12.17
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Tetracyclines• Includes doxycycline, chlortetracycline• Binds to 30S subunit• Interferes with aminoacyl-tRNA binding to A site
Fig. 35.9
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Macrolide antibiotics
Fig. 35.11
Erythromycin
• Includes clindamycin, azithromycin• Binds 23S rRNA of 50S subunit• Inhibits peptide chain elongation
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Aminogycosideantibiotics
• Includes streptomycin, gentamicin,neomycin, tobramycin, kanamycin
• Binds to 30S subunit• Inhibits protein synthesis• Causes misreading of mRNA Fig. 35.10