FRNSC 420 - EXAM 3 PRACTICE QUESTIONS AND ANSWERS (100% PASS)
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Module
FRNSC421W /FRNSC 420
Institution
FRNSC421W /FRNSC 420
FRNSC 420 - EXAM 3 PRACTICE QUESTIONS AND
ANSWERS (100% PASS)
electrophoretic mobility shift assay (EMSA) - Answer️️ -demonstrates if a
protein is bound to DNA
- fragment is placed in non-denaturing polyacrylamide gel (native PAG) to keep
protein associated to DNA
- DNA/protein complex mo...
eukaryotic RNA polymerase - Answer✔️✔️-three different polymerases, each with
their respective five subunits
- Pol II: most active, transcribes most genes
- Pol I: transcribes larger rRNA precursors
- Pol III: transcribes tRNA genes, small mRNAs, and 5S rRNA gene
DNA foot-printing - Answer✔️✔️-demonstrates if and where a protein is bound to
DNA
- protein acts as a barrier against cleavage (from either DNase or reagents of the
assay); DNA outside the DNA/protein region is susceptible to cleavage
- denaturing polyacrylamide gel (Urea-PAGE) gel to keep the protein separated
from the unbound DNA; allows the protein to protect only the DNA its bound to &
prevent it from affecting the DNA mobility
- nuclease will cleave DNA into random fragments in unpredictable patterns,
avoiding the DNA/protein complex
- a 'footprint' will appear in gel with a region of no bands within a lane of
fragments
- having a control lane allows for visualization of where the protein may be bound
DNA replication vs RNA transcription - Answer✔️✔️-- dNTPs in replication, rNTPs
in transcription
- RNAPs initiate transcription without a primer, but can only transcribe a subset of
the DNA template
- product is ssRNA
- multiple transcription events can occur sequentially from the same gene
- RNA transcription is less accurate than DNA replication
RNAP proofreading - Answer✔️✔️-lowered RNAP infidelity may affect gene
expression and protein function
- pyrophosphorolytic editing: enzyme uses its active site to catalyze removal of
incorrect rNTP through reincorporation of PPi
- hydrolytic editing: backtracks and cleaves RNA product by exonuclease-like
hydrolysis, stimulated by Gre factors
describe the structure, important features, and nomenclature of the region of target
DNA around the site of transcription initiation - Answer✔️✔️-transcription begins at
the +1 transcription start site (TSS)
- upstream (before) the TSS does not get transcribed; includes proximal
(promoter/operator) elements that aid in initiating transcription
- upstream is negative because it's moving against the direction of transcription
- downstream region moves in a positive direction (same direction as transcription)
and is transcribed
consensus promoter sequence - Answer✔️✔️-promoter sequences are highly
conserved 'landing zones' for RNAP to bind
- most conserved sequences are the -35 bp and the -10 bp sequences
- defines the binding affinity and strength RNAP has to the sequence
- RNAP is specific, may not bind as well to discrepancies in consensus sequence
- closer the promoter is to the consensus sequences, the stronger the association of
the holoenzyme to the binding sites
RNAP σ factor - Answer✔️✔️-segments bind to -10 and -35 promoter regions
3
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