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This Week. Score Conjugation Plates, Start High Frequency of Recombination (HFR) experiment, Continue Nasonia experiment. H igh F requency of R ecombination (Hfr). ...bacteria exhibiting a high frequency of recombination ,

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This week
This Week

  • Score Conjugation Plates,

  • Start High Frequency of Recombination (HFR) experiment,

  • Continue Nasonia experiment.


H igh f requency of r ecombination hfr
High Frequency of Recombination(Hfr)

...bacteria exhibiting a high frequency of recombination,

  • an alteration DNA sequence such that the genotype of subsequent individuals differs from the parent,

    …specifically, strains with a chromosome integrated F factor that is able to mobilize and transfer part of the chromosome to the F- cell.


Hfr cells

...F factor integration site,

...host (bacteria chromosome) integration site.

Hfr Cells

F factor

Bacterial Chromosome

Inserted F plasmid





Recombination requires crossing over

Double Crossover

Recombination Requires Crossing over



This week

F factor inserts in different regions of the bacterial chromosome,

Also inserts in different orientations.


Origin of replication
Origin of Replication chromosome,

Hfr Order of transfer

strain

H thr azi ton lac pur gal his gly thi

1 thr thi gly his gal pur lac ton azi

2 lac pur gal his gly thi thr azi ton

3 gal pur lac tonazi thr thi gly his


This week

Indicates direction of transfer. chromosome,

A

a

A

F factor

A

a

Hfr

F-

Hfr DNA that is not incorporated in the F- strand, and DNA that has crossed out of the F- strand is digested.


This week

A chromosome,

A

Hfr

F-

F factor

A transfers first.

A

A

Hfr

F-

A transfers last.

Leading Gene: the first gene transferred is determined empirically.


This week

Hfr Order of transfer chromosome,

strain

H thr azi ton lac pur gal his gly thi

1 thr thi gly his gal pur lac ton azi

2 lac pur gal his gly thi thr azi ton

3 gal pur lac tonazi thr thi gly his


E coli map
E. coli Map chromosome,

  • 0 minutes is at the threonine,

  • 100 minutes is required to transfer complete genome,