Biochem Genetics DNA Replication - Comp Exam Study guide.txt

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rincrocci
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Biochem Genetics DNA Replication - Comp Exam Study guide.txt
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2014-11-17 21:05:40
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Biochem Genetics DNA Replication Comp Exam Study guide
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Biochem Genetics DNA Replication - Comp Exam Study guide
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  1. ?Issues to be resolved during DNA replication
    • 1. mechanism must exist for DNA to unwind and be STABLE in open position: helicase and ssBP
    • 2. Unwinding and synthesis create tension further down helix which needs to be reduced: topoisomerases
    • 3. Primer needs to be synthesized for polymerization to start: primase
    • 4. Both strands synthesized simultaneously, but in different manners (continuous w/leading and lagging): DNA polymerase III, replisome, okazaki fragments
    • 5. RNA primer must be removed prior to completion of replication: DNA polymerase I
    • 6. Gaps between strands must be filled: ligase
    • 7. DNA needs to be proofread for errors: DNA polymerase I and III
  2. How to help telomeres from shortening the DNA replicating strands
    Telomerase: binds to the end GGTTT sequences with complementary bps, allowing the 3’ end DNA template to NOT create the hairpin loop, thereby allowing the complementary strand to FINISH replication
  3. DNA replication in prokaryotes
    • circular shape molecule, up to few mil. bps
    • SINGLE origin of replication
    • replication BIdirectional
    • Both strands replicated simultaneously
    • meeting/terminating at ter sites, producing 2 circular molecules
    • about 20min
  4. DNA Replication in eukaryotes
    • MULTIPLE LINEAR DNA molecules (1 per chromosome), each millions of bps
    • Multiple ori's
    • need special mechanisms to fully replicate ENDS of each molecule
    • several hours
  5. Process and Proteins involved
    • 1)Helicases unstabalize the helix opening up the DNA
    • 2) Single strand binding protiens hold the helix in the open position
    • 3) Topoisomerases (DNA Gyrase) relieves tension from supercoiling ahead of the helix
    • 4) Primase – Synthesizes and lays down an RNA primer so DNA polymerase can begin synthesizing DNA
    • 5) DNA Polymerase III begins synthesizing new DNA in the 5’-3’ Direction
    • 6) Leading strand is direct but lagging strand done in small pieces – Okazaki fragments
    • 7) DNA polymerase I – removes RNA primers and fills in space with DNA
    • 8) DNA Ligase joins the phosphate backbones of the various fragments (fills in the nicks)
    • 9) All DNA polymerase contain 3’-5’ exonuclease activity allowing for proofreading and synthesizing of DNA in 5’-3’ direction

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