BIOC0005 SECTION 2 EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS VERIFIED
Which experiment showed that RNA polymerase binds to promoter in
prokaryotes (-35 ~ -10)?
DNAase footprinting experiment. Used chemical cleavage (type of DNA sequence)
Which experiment showed that RNA pol was composed of multiple subunits
Cellulose acetate chromatography showed RNA pol had sigma factor + 2 alpha + beta +
beta'
Describe the function of the RNA pol subunits
sigma - binds to promoter region (-35)
alpha - assembly, interacts with DNA and transcription factors
beta - DNA and RNA binding, RNA synthesis
beta' - DNA binding and RNA synthesis
Holoenzyme means
whole enzyme (for RNAP means all subunits present
2 key region and function of promoter
-35: sigma recognises to specific base sequence
-10: orients the RNAP
Consensus sequence for sigma 70 for -35 and -10
TTGACAT
TATAAT
, Consensus sequence for lac operon -35 and -10
TTTACAC
TATGTT
2 types of termination
1. intrinsic (Rho-independent)
2. Rho dependent
Explain Rho-independent termination
- 2 GC rich regions which form stem loop when translated
- stretch of Us (forms weak H-bonds)
- A:U bonds are weak so RNAP released when DNA deforms
Explain Rho-dependent
- Requires Rho (hexamer) a helicase
- When stop codon reached and ribosome disattaches Rho attaches to mRNA at rho
utilization site (rut)
- Rho stalls near hairpin and uses ATP to breakdown H-bonds
Operon definition
Cluter of similar functioning proteins which forms a polycistronic mRNA
lac operon sequence (5)
promoter
operon
lac z
lac y
lac a
WITH COMPLETE SOLUTIONS VERIFIED
Which experiment showed that RNA polymerase binds to promoter in
prokaryotes (-35 ~ -10)?
DNAase footprinting experiment. Used chemical cleavage (type of DNA sequence)
Which experiment showed that RNA pol was composed of multiple subunits
Cellulose acetate chromatography showed RNA pol had sigma factor + 2 alpha + beta +
beta'
Describe the function of the RNA pol subunits
sigma - binds to promoter region (-35)
alpha - assembly, interacts with DNA and transcription factors
beta - DNA and RNA binding, RNA synthesis
beta' - DNA binding and RNA synthesis
Holoenzyme means
whole enzyme (for RNAP means all subunits present
2 key region and function of promoter
-35: sigma recognises to specific base sequence
-10: orients the RNAP
Consensus sequence for sigma 70 for -35 and -10
TTGACAT
TATAAT
, Consensus sequence for lac operon -35 and -10
TTTACAC
TATGTT
2 types of termination
1. intrinsic (Rho-independent)
2. Rho dependent
Explain Rho-independent termination
- 2 GC rich regions which form stem loop when translated
- stretch of Us (forms weak H-bonds)
- A:U bonds are weak so RNAP released when DNA deforms
Explain Rho-dependent
- Requires Rho (hexamer) a helicase
- When stop codon reached and ribosome disattaches Rho attaches to mRNA at rho
utilization site (rut)
- Rho stalls near hairpin and uses ATP to breakdown H-bonds
Operon definition
Cluter of similar functioning proteins which forms a polycistronic mRNA
lac operon sequence (5)
promoter
operon
lac z
lac y
lac a
