John 15:4
4
Abide in me, and I in you. As
the branch cannot bear fruit
of itself, except it abide in the
vine; no more can ye, except
ye abide in me
©2001 Timothy G. Standish
Recombination
Timothy G. Standish, Ph. D.
©2001 Timothy G. Standish
Types Of Recombination
Generalized or Homologous Recombination - Occurs
during prophase of meiosis I and involves exchange
between homologous strands of DNA
Site Specific Recombination - Short homologous
sections of bacterial and phage DNA serve as a site for
recombination and thus incorporation of phage DNA into
bacterial chromosomes
Copy choice - Used by RNA viruses, polymerase switches
back and forth between templates from different parents
Transposition - Not truly recombination between
different genomes, but the movement of transposons
within a genome
©2001 Timothy G. Standish
Homologous Recombination
In Eukaryotes
Prophase I
Replication
E
E
e
e
e
E
e
N
N
E
Telophase I
N
n
n
N
E e
N N
n n
Telophase II
n
As long as genes on the same
n
chromosome are located a
long distance apart, they will
assort independently due to
crossing over during
prophase I of meiosis
E e
E
e
E
e
N
N
n
n
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
Homologous chromosomes
Meiosis Prophase I
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
Exonuclease
Double strand break
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
Exonuclease
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
Exonuclease
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
Exonuclease
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
DNA
Polymerase
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
DNA
Polymerase
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
DNA
Polymerase
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
DNA
Polymerase
©2001 Timothy G. Standish
The Current Eukaryotic
Recombination Model
Ligase
Branch migration
Ligase
©2001 Timothy G. Standish
Holliday Structure
©2001 Timothy G. Standish
Holliday Structure
Bend
©2001 Timothy G. Standish
Holliday Structure
Bend
Twist
©2001 Timothy G. Standish
Holliday Structure
Cut
©2001 Timothy G. Standish
Holliday Structure
Cut
Heteroduplex
region
Recombinant
Strand
©2001 Timothy G. Standish
Holliday Structure
Cut
©2001 Timothy G. Standish
Holliday Structure
Cut
Heteroduplex
region
Recombinant
Strand
©2001 Timothy G. Standish
Holliday Structure
©2001 Timothy G. Standish
Cutting The Holliday Structure
©2001 Timothy G. Standish
Four Possible Outcomes
Pink
Blue
Cut
Cut
Cut
Cut
Heteroduplex
Pink
Blue
Heteroduplex and a short recombinant area between cuts
©2001 Timothy G. Standish
Four Possible Outcomes
Cut
Blue
Pink
Cut
Cut
Cut
Blue
Heteroduplex
Pink
Heteroduplex with no recombinant area between cuts
©2001 Timothy G. Standish
Four Possible Outcomes
Cut
Cut
Cut
Cut
Blue
Pink
Pink
Blue
Recombinant chromosomes joined by heteroduplex between cuts
©2001 Timothy G. Standish
Four Possible Outcomes
Cut
Cut
Cut
Cut
Pink
Blue
Blue
Pink
Recombinant chromosomes joined by heteroduplex between cuts
©2001 Timothy G. Standish
©2001 Timothy G. Standish