The F plasmid and conjugation Insertion sequences IS2, Is3(2 copies ), 1s1000 F factor: 100kb DNA F bacterium Genes involved in making F pili and in the transfer of dna Target site for Genes involved in singlestrand replication etc DNase
The F plasmid and conjugation 1. F pilus extends and binds to F cell wall. F 2. on contact F pilus with F- cell pilus retracts Cells are drawn together. Passageway forms between cells COrO 4. Cells separate at 3. DNase cuts plasmid completion of DNA at target site. transfer and synthesis Single strand moves Both are now f+ and across corridor. F can conjugate with other cell synthesizes F cells complementary strand.Ft cell replaces transferred strand
Generation of an Hfr strain a single crossover between the F-factor and the bacterial chromosome This generates a high frequency recombination cell (Hfr) Recombination occurs at site of insertion sequence
Generation of an Hfr Strain • a single crossover between the F-factor and the bacterial chromosome • This generates a high frequency recombination cell (Hfr). • Recombination occurs at site of insertion sequence
The Hfr strain transfers a copy of the bacterial chromosome along with the F-factor. If mating is interrupted, only a portion of the chromosome is transferred The location of a gene can be determined by determining when it is transferred
• The Hfr strain transfers a copy of the bacterial chromosome along with the F -factor. • If mating is interrupted, only a portion of the chromosome is transferred. • The location of a gene can be determined by determining when it is transferred
Making an Hfr chromosome F plasmid Target site for singlestrand dNase IS3-x Same Is3s on plasmid and chromosome Chromosome Ts3 in Ft cell S3 1s3 Chromosome in Hfr cell Insertion of Resulting F plasmid Hfr strain (b) F+recipient chromosome B