F and partial diploids The f-factor in a hfr chromosome can excise out to become an autonomously replicating plasmid If a segment of the chromosome becomes part of the F plasmid during excision, the new element is called an F plasmid. This F'-plasmid can be conjugated to another bacterial cell to form a partial diploid F'-plasmid F-plasmid Hfr chromosome Recombination chromosome \point with deletion
F’ and partial diploids • The F-factor in a Hfr chromosome can excise out to become an autonomously replicating plasmid. • If a segment of the chromosome becomes part of the Fplasmid during excision, the new element is called an F’- plasmid. • This F’-plasmid can be conjugated to another bacterial cell to form a partial diploid. F-plasmid F’-plasmid chromosome with deletion Recombination point Hfr chromosome a a a
Partial Diploids in bacteria are used in complementation analysis Bacterial cells E (by either conjugation or transformation) F plasmid he recipient bacterial cells are recA- to prevent recombination and re-integraton of the plasmid into the host Partial diploid chromosome for only one region of the chromosome
Partial Diploids in bacteria are used in complementation analysis a F’ plasmid + Bacterial cells = (by either conjugation or transformation) a a Partial diploid for only one region of the chromosome The recipient bacterial cells are recA- to prevent recombination and re-integraton of the plasmid into the host chromosome
TABLE 13.2 Comparing the Conjugational cycles of F, Hfr, and F Cells In an F Cell In an Hfr Cell In an F cell Donor and F plasmid F plasmid Recipient before Conjugation F F Events of Conjugation Donor and Recipient after OOOOOO(O⊙oo Conjugation F partial diploid Merozygote transient) Comments Efficient transfer of Ffactor; poor Transfer of entire F factor only Efficient transfer of F element, transfer of bacterial genes inefficiently. Efficient transfer of which includes a few bacterial bacterial genes, but requires an genes, generating stable partial even number of crossovers diploids. Poor transfer of other in recipient chromosomal genes
Bacteriophage Genetics Phage can take two different pathways upon infection of a bacterial cell lytic or lysogenic
Bacteriophage Genetics Phage can take two different pathways upon infection of a bacterial cell : lytic or lysogenic
Generalized Transduction client donor introduction of genes from a donor cel occurs with phage which can Co-package DNA (rare event a Packaged dNa is a random fragment b b Used to measure: co-transduction frequencies map distances
Generalized Transduction • introduction of genes from a donor cell • occurs with phage which can co-package DNA (rare event) • Packaged DNA is a random fragment • Used to measure: • co-transduction frequencies • map distances a- b- c- a+ b+ c+ recipient donor
Generalized A、 Phage particle transduction infects host a Host DNA fragment bearing e Agene C is packaged in phage. Viral components are assemblea s Host DNA is broken into fragment Cells lyses, phages released Phage infects another bacterial host (recipient). Recombination between injected DNA and host chromosome cC Resulting C+ transductant
Gene mapping by cotransduction Donor: thyA+ lysA+ CySC+ make P1 lysate infect recipient Recipient: thy 7A" lysA- cySC Selected marker Unselected marker th 47%lys*, 2% cys*+ lys 50%thy; 0% cys+ (b) IVsA thy cysc
Temperate bacteriophage E coli cell -Lytic cycle Lysogenic cycle Cell lyses Circular phage chromosome Recombination site Prophage Lysogenic bacteric
Phage lambda K48 kb Phageλ circularized in host cell after infection Linear phage i chromosome itt in the bacteriophage particle Attachment sites bio E coli chromosome Integration att gal prophage
Phage lambda
1易 Phage i infect wildtype bacteria Wildtype bacteria ambda lysogen cell Turbid plaques on lawn of bacteria Microcolonies of Infect cells with phage 7 lysogenic bacteria present within turbid plaque Absence of plaques; no phage 7 lysis
