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7 Cards in this Set
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- 3rd side (hint)
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Bacterial Genome Construction Methods |
Central Dogma - DNA->RNA->protein , repli-transcrip-translat Binary Fission (cell division): Dna repli (forms 2 daughter chromo), cell elongation, septum formation + completion=> cell separation Supercoiling: Allows tight packing of DNA +ve-turns added, -ve turns removed Relaxed circular->relaxed nicked circular->supercoiled circular->supercoiled domains Important end = topoisomerase topo I -> removes -ve supercoils Topo II=DNA gyrase topo IV-> releases DNA + introduces +ve supercoils |
3 methods Central Dogma Binary Fission Supercoiliing |
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DNA Synthesis |
Leading: -Primer gives 3’-OH=> initiates synth -DNA Pol works 5’->3’ continuously Lagging: RNA primer allows DNA pol I to work 3’->5’ => discontinuous DNA pol III - removes primer, fills in gaps + proof reads (replaces mismatched nucleo’s w correct ones) Replisome: -complex struct carries out DNA repli -enz’s = DNApol III, DNA helices, DNA gyrase (topoII), DNA primase, DNA pol III |
DNA synth: leading and lagging strand Replisome |
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Circular DNA Replication |
dual repli forks work at origin (12oclock) work down to 6 o’clock -> FtsZ ring froms at mid cell before separation => 2 daughter chromos linked like chain => daughter chromos unlinked! MIN proteins (C,D,E) facilitate location of FtsZ ring Bacterial Cell Div proteins: FtsZ-> initiates cell div, ring shape FtsA->ATP hydrolysing, energy provider ZipA->anchors Z-rig to cell membrane FtsI-> penecillin binding protein=> synth septal peptidogylcan FtsK->DNA translocate |
Mechan Bacterial cell div proteins + function (5 proteins) |
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Horizontal Gene Transfer (HGT) Overview |
What? -Gene transfer from one independent organism to another (same or diff species) -transformation, transduction, conjugation 2 pathways result in reproduction then produce stable recombinants: 1-integration of donor DNA into partially diploid cell 2- donor DNA self-replicates 2 pathways result in NO stable recombinants: 1-donor DNA CANT self replicate-> recipient reproduces but donor DNA DOESNT 2-cell doesnt recognise DNA-> host restriction |
What is it? mechanism? 2 possible outcomes? |
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HGT - Transformation, Transduction |
TRANSFORMATION What? donor DNA integration into recipient cell => genetic change Natural - cell competence regu in naturally transformable bacteria - DNA binding, DNA donor uptake into recipient cell, RecA mediated homologous recombination=> transformed recipient cell (confers phenotypic trait) Artificially - forced cell competence e.g by electroporation (electric shock) TRANSDUCTION What? DNA transfer by bacteriophage Generalised - DNA from any part of host genome packed inside virion -low transducing efficiency Specialised - DNA from spec region of host chromo integrated to virus genome -(norm event)phage DNA circulises, detaches from host DNA, repli, lysis=> normal phage -(rare event) portion of host DNA exchanged for phage DNA, repli, lysis=> defective phage that can transduce galactose genes !!
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HGT - Conjugation |
What? Genetic transfer that involves cell to cell contact through plasma-encoded mechanism Requirement? F-plasmid -contains DNA replication regulatory genes, transposable elements + tra genes F+ cell - contains chromo DNA +F plasmid F- cell - chromo + NO F plasmid Hfr cell=conjugative plasmid integrated into its chromo DNA
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Bacterial Genome Evo - Mutations, Mutagenesis, Transposable Elements |
MUTATIONS Induced, spontaneous or point point - 1bp change silent (no effect), missense (amino change=>protein change), non-sense (stop produced), frameshift (delete/insert) - reversible! Same-site revertant=mutant at same site as original mutation, 2nd-site=diff site -supressor = 2nd mutation that compensates for effect of first Ames test - detects increase mutation rate in bacteria in presence of suspected mutagen => detects potentially harmful chemicals MUTAGENESIS Physical - non-ionising=UV , ionising=X-rays cause single/double/triple mutations -e.g. UV signature= single C->T or double CC->TT Chemical - chemicals (nitric acid), base analogues (halouracils/uridines), alkylating agents (mono or bifunctional) , intercalators cause. Point mutations Transposon - class I=retrotransposons, class II=act through rolling-circle repli or cut and paste mechan TRANSPOSABLE ELEMENTS Insertion seq’s e.g. IS2 - about 1000 bps long, inverted repeats aboutt 10-50 bps transposons e.g. Tn5, Tn10 - longer than insertion seqs, insertion generates duplicate target seq, many indicate antibiotic resistance |
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