Bacterial conjugation

Fertility (F) factor

a plasmid that gives the bacterial cell the ability to produce pili

Hfr strain

a bacterial strain in which the F factor is INTEGRATED into the chromosome

What happens in Hfr x F- cross

1. None* of the F- recipient strains are converted into WHAT nor WHAT

• this would require copy and transfer of WHAT

2. The integrated F factor (in the Hfr strain), drives transfer of some (rarely all) of the WHAT

3. The donor chromosomal fragment can WHAT with the recipient chromosome

What happens in Hfr x F- cross

1. None* of the F- recipient strains are converted into F+ nor Hfr strains

• this would require copy and transfer of ENTIRE GENOME

2. The integrated F factor (in the Hfr strain), drives transfer of some (rarely all) of the BACTERIAL CHROMOSOMES

3. The donor chromosomal fragment can RECOMBINE with the recipient chromosome

Bacterial conjugation

• The integrated F factor (in the Hfr strain), drives transfer of some (rarely all) of the WHAT

• DNA replication and transfer begin where the WHAT was integrated

• Transfer starts at the WHAT

Bacterial conjugation

• The integrated F factor (in the Hfr strain), drives transfer of some (rarely all) of the BACTERIAL CHROMOSOMES

• DNA replication and transfer begin where the F FACTOR was integrated

• Transfer starts at the ORIGIN OF TRANSFER

Exoconjugant

Cell that contains a fragment of donor DNA; has participated in conjugation

Lastly, the donor chromosomal fragment can WHAT (randomly) with the recipient chromosome

Lastly, the donor chromosomal fragment can RECOMBINE (randomly) with the recipient chromosome

Bacterial conjugation - as a gene mapping tool

Interrupted mating experiments

Interrupted mating experiments

Disrupt conjugation at fixed time intervals to see which genes get transferred

Interrupted mating experiments tell you gene

• WHAT

• WHAT

Interrupted mating experiments tell you gene

• Order

• Spacing

F plasmid can integrate at different WHAT and in different WHAT therefore different interrupted mating experiments will give different WHAT

F plasmid can integrate at different SITES and in different ORIENTATIONS therefore different interrupted mating experiments will give different RESULTS

Gene order of entrance will indicate WHAT and WHAT of F factor

Gene order of entrance will indicate LOCATION and DIRECTION of F factor

Recombination can take place between a WHAT (WHAT) and a WHAT (WHAT) (any double-stranded DNA that is WHAT) - DNA transferred by conjugation

Recombination can take place between a COMPLETE GENOME (ENDOGENOTE) and a PARTIAL GENOME (EXOGENOTE) (any double-stranded DNA that is HOMOLOGOUS) - DNA transferred by conjugation

In recombinant bacteria a single crossover cannot produce a WHAT recombinant

In recombinant bacteria a single crossover cannot produce a VIABLE recombinant

To keep the circular genome intact, there must be an WHAT number of recombination events

To keep the circular genome intact, there must be an EVEN number of recombination events

Linear fragment is loss to WHAT

Recombinants intact WHAT

Linear fragment is loss to EXONUCLEASES

Recombinants intact CIRCULAR GENOME

The closer the two genes are together on the chromosome, the less likely a WHAT event will occur WHAT them

The closer the two genes are together on the chromosome, the less likely a CROSSOVER event will occur BETWEEN them

Interrupted mating

• Tracking the time of marker entry to generate a WHAT (in units of WHAT)

Interrupted mating

• Tracking the time of marker entry to generate a CHROMOSOMAL MAP (in units of MINUTES)

Recombination frequency

• Crossing-over in different regions generates different WHAT, allowing us to WHAT between genes (in units of WHAT)

Recombination frequency

• Crossing-over in different regions generates different RECOMBINANTS, allowing us to ESTIMATE DISTANCE between genes (in units of cM)