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Eva Lee - 2007
DNA Replication, Repair & Recombination
25
Medical
Professional
09/12/2007

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Cards

Term
What is different about lagging strand DNA polimerization in bac vs. mammals?
Definition
- in bac, only α-subunit of DNA pol III
- in mammals, pol δ & α on lagging (pol ε for leading)
- mammalian primase forms tight complex with pol α while bacterial primase associated with helicase forming primosome
Term
What are the components of the DNA pol III holoenzyme (bacteria)?
Definition
- pol III core (2 copies)
- β sliding clamp
- γ/τ complex clamp loader
Term
Components of the (bacterial) replisome?
Definition
- holoenzyme
- DnaG Primase
- DnaB (helicase)
- SSB
Term
What 3 steps give rise to high-fidelity DNA synthesis?
Definition
1) 5'-> 3' polumerization
2) 3'-> 5' exonucleolytic proofreading
3) Strand-directed mismatch repair
Term
Helicase function and name in mammals
Definition
opens DNA at fork; MCM Proteins
Term
Primase
Definition
RNA-DNA primer synthesis for subunit of pol α-primase
- primase-pol α
Term
Polymerase function and types in mammals
Definition
elongates DNA; pol δ and ε
Term
Proofreading exonuclease function and names in mammals
Definition
3' -> 5' nuclease; pol δ and ε
Term
Sliding Clamp function & name in mammals
Definition
processivity factor for pol δ and ε; PCNA
Term
Clamp loader (function and name in mammals)
Definition
Load PCNA, polymerase switching
- RF-C
Term
Single STrand DNA binding protein (Funciton and name in mammals)
Definition
Protect single-stranded DNA; RP-A
Term
DNA Ligase I (Func and name in mammals)
Definition
Ligates DNA pieces (Lig 1)
Term
DNA topoisomerase (func & name in mammals)
Definition
removes DNA topological contraints (Top I & II)
Term
The bacterial primosome contains what two enzymes?
Definition
Helicase and primase
Term
Pol III and Pol δ are high processivity polymerases in E.coli and mammals, respectively.
Definition
True
Term
Name a few human polymerases? Which have proof reading activity?
Definition
Pol δ and pol ε are major replicative polymerases. Pol β, γ, and ε have proof reading capabilities.
Term
Which human polymerase is responsible for leading strand synthesis and which for the bulk of synthesis?
Definition
Pol ε is leading and Pol δ polymerizes bulk of DNA.
Term
What are the 3 steps of Okazaki Frament processing?
Definition
1) removal of primer
2) synthesis of DNA across gap
3) DNA ligation
Term
Do any eukaryotic DNA polymerases carry 5' -> 3' exonuclease activity?
What 2 exonucleases repair human DNA?
Definition
RNase H removes ribonucleotides at all locations except the 5' end. FEN1 removes the last ribonuclotide and several deoxynuleotides.
Term
What is the human equivalent of SSB and what the its functions?
Definition
Replication Factor-A (RF-A), HSSB, etc.
- Stabilizes unwound ssDNA
- binds to ssDNA w/ocovering bases
- remove "hairpin"
Term
Slinding clamps. Names and function in E.coli and humans...
Definition
- Protein rings that encircle DNA
- keep polymerases firmly on DNA when moving but releases once hits dsDNA.
- in E.coli - β subunit of DNA pol III
- in humans - proliferating cell nuclear antigen (PCNA)
- req for leading/lagging synth.
Term
Clamp Loading Proteins
Definition
- ATPase activity involved in attaching the clamp.
- released once polymerase binds to clamp.
- called RF-C in humans
Term
DNA ligases
Definition
- DNA ligase I joins Okazaki frags.
- join segments
Term
DNA Topoisomerases
Definition
- prevents DNA tangling
- Type I - introduces single-strand breaks
- Type II - dbl strand breaks
- TopoII for daughter chromosome separation
Term
What is the telomerase and what are its components? Where is telomerase switched on and off?
Definition
- The telomerase is a reverse transcriptase enzyme.
- it's a protein-RNA complex
- RNA component is complementary to the telomeric single strand overhand and is a template for telomeric DNA (TTAAGGG)
- The protein component is hTERT (human telomere reverse transcriptase) which provides the catalytic activity
- on in germ cells
- off in somatic cells
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