BBlecture10S09s - gex1 Principles of Bacterial Genetics...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: gex1 Principles of Bacterial Genetics Principles (genetic exchange in prokaryotes) 11.9: 11.9: 11.10: 11.11: 11.11: 11.12: 11.12: 11.13: Genetic Recombination Genetic Transformation Transduction Transduction Conjugation: Essential Features The Formation of Hfr Strains and The Chromosome Mobilization Chromosome 11.14: Complementation 11.15: Gene Transfer in Archaea 11.16: Mobile DNA: Transposable Elements genetic recombination: genetic • SSB – single stranded binding protein • RecA-like proteins found in all prokaryotes, yeast, higher eukaroytes examined gex2 • resolution involves nuclease and DNA ligase activities (Fig 11.13, 12th ed) A B gex2a fret not; for illustration only! a A b B A B chi form a isomerize b resolution A B A b a resolution b b patch a a B exchange of flanking markers (splices) DNA transfer: DNA gex3 transduction: transfer of host genes from one host to another by a virus (Fig 11.12, 12th ed) transformation: transfer of bacterial genes involving free DNA conjugation: transfer of genes from one prokaryotic cell to another by mechanism involving cell-to-cell contact and a plasmid search for a rare genetic recombinant amongst nonrecombinants is based on selectable markers: nonrecombinants gex4 (Fig 11.14, 12th ed) Griffith’s experiment with pneumococcus (now Streptococcus pneumoniae): Streptococcus gex5 (Fig 11.15, 12th ed) S: “smooth” colony morphology (encapsulated) R: “rough” colony morphology (no capsule) transformation: transformation • requires competent cells (or electroporation) gex6 (Fig 11.16, 12th ed) generalized transduction: generalized • host DNA derived from virtually any part of host genome can be involved gex7 (Fig 11.17, 12th ed) specialized transduction: transduction • DNA involved is from a specific region of host genome only gex8 (Fig 11.18, 12th ed) genetic map of the F plasmid: genetic genes involved in conjugative transfer gex9 (Fig 11.19, 12th ed) transfer of plasmid DNA by conjugation: conjugation gex10 (Fig 11.21(a), 12th ed) contact between two conjugating bacteria: contact gex10a + fimbriae F cell (Fig 11.20, 12th ed) • initiated via pilus • retraction of pilus within donor cell draws two cells together • transfer of DNA occurs once mating pair drawn together replication and transfer process: replication gex11 (Fig 11.21(b), 12th ed) integration of F plasmid into chromosome: integration gex12 Hfr cells: high frequency of recombination • cells with chromosomeintegrated F plasmid (Fig 11.22, 12th ed) • breakage of Hfr chromosome at OriT • beginning of transfer to F- recipient gex13 (Fig 11.23, 12th ed) transfer of chromosomal DNA by conjugation: transfer gex14 recombination of donor DNA into recipient chromosome (Fig 11.24, 12th ed) different Hfr strains: different • circular bacterial chromosome can open at various insertion sequences at which the F plasmids become inserted gex15 (Fig 11.25, 12th ed) Joshua Lederberg Joshua Lederberg & Tatum (1946) • do bacteria have sex? gex15a • “plasmid” to describe apparently extrachromosomal genetic elements (1950s) Zinder & Lederberg (1952) • transduction Nobel Prize (1958) for work in bacterial genetics 2005 - Lederberg still conducted lab research on bacterial & human genetics; advised government & industry on global health policy, biological warfare, & threat of bioterrorism (Profiles in Science: ) • procedure to detect genetic conjugation: procedure gex16 (Fig 11.26, 12th ed) gex17 rate of recombinant formation after mixing Hfr & F- bacteria: rate (Fig 11.27, 12th ed) gex18 complementation analysis: analysis • both gene A & gene B products required for Trp+ phenotype (Fig 11.28, 12th ed) gene transfer in Archaea: gene • limited knowledge - practical problems! • extreme incubation conditions may be required • unaffected by many “usual” antibiotics → limited availability of selectable markers for genetic crosses • isn’t one model organism → scattered work & knowledge (extreme halophiles, methanogens) • examples of transformation, viral transduction, conjugation known • mechanism(s) of conjugation probably differ from what is seen in Bacteria • several plasmids been isolated gex19 maps of transposable elements: maps gex20 (Fig 11.30, 12th ed) gex21 the transposition process: the • note origin of duplicated target sequence (Fig 11.31, 12th ed) mechanisms of transposition: mechanisms gex22 (Fig 11.32, 12th ed) transposon mutagenesis: transposon gex23 (Fig 11.33, 12th ed) ...
View Full Document

This note was uploaded on 02/04/2011 for the course BIOL 140 taught by Professor Bb during the Spring '11 term at University of Warsaw.

Ask a homework question - tutors are online