©2001 Timothy G. Standish John 15:4 4Abide 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 Father Mother e n E N Telophase II E NN e E nn e E N n e Replication e n E N Prophase I E N N n e n As long as genes on the same chromosome are located a long distance apart, they will assort independently due to crossing over during prophase I of meiosis Telophase I N e E N E n e n

©2001 Timothy G. Standish The Current Eukaryotic Recombination Model Meiosis Prophase I Homologous chromosomes

©2001 Timothy G. Standish The Current Eukaryotic Recombination Model Double strand break Exo- nuclease

©2001 Timothy G. Standish The Current Eukaryotic Recombination Model Exo- nuclease

©2001 Timothy G. Standish The Current Eukaryotic Recombination Model Exo- nuclease

©2001 Timothy G. Standish The Current Eukaryotic Recombination Model Exo- nuclease

©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

©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 Recombinant Strand Heteroduplex region

©2001 Timothy G. Standish Holliday Structure Cut

©2001 Timothy G. Standish Holliday Structure Cut Recombinant Strand Heteroduplex region

©2001 Timothy G. Standish Holliday Structure

©2001 Timothy G. Standish Cutting The Holliday Structure

©2001 Timothy G. Standish Four Possible Outcomes Cut Heteroduplex and a short recombinant area between cuts Blue Pink Heteroduplex

©2001 Timothy G. Standish Four Possible Outcomes Cut Heteroduplex with no recombinant area between cuts Blue Pink Heteroduplex

©2001 Timothy G. Standish Four Possible Outcomes Cut Recombinant chromosomes joined by heteroduplex between cuts PinkBlue Pink

©2001 Timothy G. Standish Four Possible Outcomes Cut PinkBlue Pink Recombinant chromosomes joined by heteroduplex between cuts

©2001 Timothy G. Standish