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BIO311: Molecular Biology

Unit 9: DNA Recombination and Transposition   Recombination and transpositions permanently alter DNA sequences. Recombination contributes to DNA repair and it increases genetic variation. Transposition events also increase genetic variation, and they can result in new domain combinations in proteins through exon shuffling.

Unit 9 Time Advisory
This unit should take you approximately 7 hours to complete.

☐    Subunit 9.1: 1.5 hours

☐    Subunit 9.2: 1.0 hour

☐    Subunit 9.3: 0.5 hours

☐    Subunit 9.4: 0.5 hours

☐    Subunit 9.5: 1.0 hour

☐    Subunit 9.6: 2.0 hours

☐    Subunit 9.7: 0.5 hours

Unit9 Learning Outcomes
Upon successful completion of this unit, students will be able to: - Describe the crossing over event during meiosis I. - Compare and contrast the Holliday and the double-stranded break models. - Compare recombination and transposition and the roles they play in genetic diversity.  - Compare and contrast genomic insertions of jumping genes and retroviruses. - Describe the consequence of genomic mobile element insertions including the McClintock experiment.  - Explain how RecA and RecBCD work during recombination. - Predict the consequence of exon shuffling in specific genes.

9.1 Recombination Events in the Cell   9.1.1 Repair of Double-Stranded Breaks   - Reading: John W. Kimball’s “DNA Repair" Link:  John W. Kimball’s “DNA Repair" (HTML)
 
Instructions: Please study the "Repairing Strand Breaks" and "Meiosis Also Involves DBSs" sections on this page.
 
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9.1.2 Genetic Variation   - Reading: John W. Kimball’s “The Evidence of Creighton and McClintock" Link:  John W. Kimball’s “The Evidence of Creighton and McClintock" (HTML)
 
Instructions: Please study this page.  Follow "Link To a Model Showing How Two DNA Molecules Can Cross Over" at the end of the page.
 
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  • Reading: John W. Kimball’s “Meiosis" Link:  John W. Kimball’s “Meiosis" (HTML)
     
    Instructions: Please study the "Meiosis I" section on this page.
     
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9.1.3 Homologous Recombination in Eukaryotes and Meiosis   - Reading: John W. Kimball’s “Meiosis" Link:  John W. Kimball’s “Meiosis" (HTML)
 
Instructions: Please study the "Meiosis I" section on this page.
 
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  • Reading: John W. Kimball’s “Crossing Over and Genetic Recombination in Meiosis" Link:  John W. Kimball’s “Crossing Over and Genetic Recombination in Meiosis" (HTML)
     
    Instructions: Please study this page.
     
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9.2 RecBCD Model in Prokaryotes   - Reading: NCBI Bookshelf: Griffiths et al.'s: "Enzymatic Mechanism of Recombination" Link:  NCBI Bookshelf: Griffiths et al.'s: "Enzymatic Mechanism of Recombination" (HTML)
 
Instruction:  Please study this page.
 
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9.3 Holliday Junction   - Reading: Web-Books.com's "The Holliday Model of DNA Crossover" Link:  Web-Books.com's "The Holliday Model of DNA Crossover" (HTML)
 
Instruction:  Please study this page.
 
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  • Web Media: YouTube: University of North Carolina: Dr. Jeff Sekelsky 's "DNA Holliday Junction" Links:  YouTube: University of North Carolina: Dr. Jeff Sekelsky 's "DNA Holliday Junction" (YouTube)
     
    Instructions: Please watch this animation (1 min).
     
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9.4 Double-Stranded Break Model   - Reading: NCBI Bookshelf: Lodish et al.'s "Recombination between Homologous DNA Sites" Link:  NCBI Bookshelf: Lodish et al.'s "Recombination between Homologous DNA Sites" (HTML)
 
Instruction: Please read the "Double-Strand Breaks in DNA Initiate Recombination" section on this page.
 
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  • Reading: MIT: Helleday et al's "Double-Strand Break Repair via Double Holliday Junctions (Szostak Model)" Link: MIT: Helleday et al's "Double-Strand Break Repair via Double Holliday Junctions (Szostak Model)" (Adobe Flash)
     
    Instruction: Please click on the question mark in the right-hand corner and follow the instructions.
     
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9.5 RecA-like Protein   9.5.1 Active Site and Function   - Reading: NCBI Bookshelf: Alberts et al.'s "Genetic Recombination" Link: NCBI Bookshelf: Alberts et al.'s "Genetic Recombination" (HTML)
 
Instruction: Please study "The RecA Protein Enables a DNA Single Strand to Pair with a Homologous Region of DNA Double Helix in E. coli" section on this page.
 
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9.5.2 Conservation in Humans   - Reading: NCBI Bookshelf: Alberts et al. "General Recombination" Link: NCBI Bookshelf: Alberts et al. "General Recombination" (HTML)
 
Instruction:  Please study the "There Are Multiple Homologs of the RecA Protein in Eucaryotes, Each Specialized for a Specific Function" section on this page.
 
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9.6 Transposition   9.6.1 Transposable Elements   - Reading: John W. Kimball’s "Transposons: Mobile DNA" Link: John W. Kimball’s "Transposons: Mobile DNA" (HTML)
 
Instruction:  Please study this page.
 
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9.6.2 DNA Transposon   - Reading: Scitable: Dr. Leslie Pray's "Transposons, or Jumping Genes: Not Junk DNA?" Link: Scitable: Dr. Leslie Pray's "Transposons, or Jumping Genes: Not Junk DNA?" (HTML)
 
Instruction:  Please study this page.
 
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9.6.3 Virus-Like Transposon   - Reading: NCBI Bookshelf: Griffiths et al.’s "Retroviruses" Link: NCBI Bookshelf: Griffiths et al.’s "Retroviruses" (HTML)
 
Instruction:  Please study this page.
 
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9.7 Exon Shuffling   - Reading: NCBI Bookshelf: Strachen and Read's "Our Place in the Tree of Life" Link: NCBI Bookshelf: NCBI Bookshelf: Strachen and Read's "Our Place in the Tree of Life" (HTML)
 
Instruction:  Please study the "Exon Shuffling Permits Diverse Combinations of Structure and Functional Modules, and May be Mediated by Transposable Elements" section on this page.  Please note that exon shuffling brings together functional domains of unrelated genes, thus it can create novel proteins with unique regulatory features.
 
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