Molecular Biology (5) Flashcards
Name the stages of prokaryotic transcription
Initiation
Elongation
Termination
How many RNA polymerases do prokaryotes have and is a primer required?
1
No
What are the components of E. coli RNA polymerase holoenzyme?
Core polymerase
Sigma factor
What are the subunits of the E. coli core polymerase and what are their roles?
α2ββ'ω α - scaffolding β - active site β' - DNA binding ω - unknown
What is the role of the sigma factor in E. coli RNA polymerase holoenzyme?
Promoter recognition for transcription initiation
How many subunits does E. coli sigma factor consist of?
4
Which is the most common type of sigma factor?
σ70
What does the 3D structure of DNA polymerase resemble?
Hand
What does the 3D structure of RNA polymerase resemble?
Crab claw
Where are the key regions of the bacterial transcription promoter site?
-10 and -35
What is the consensus sequence at -35 nucleotides?
TTGACA
What is the consensus sequence at -10 nucleotides?
TATAAT (TATA box sequence)
What is the effect of the -10/-35 region being closer to the consensus sequence?
Stronger RNA polymerase binding
Which sigma factor binds to the -10 region?
σ2
Which sigma factor binds to the -35 region?
σ4
What is the significance of the -10 region?
Initial site of DNA melting in active site
Where, when, and why does the α subunit bind?
UP element - upstream of -35 region
For genes regularly transcribed - e.g. housekeeping genes
Gives stronger RNA polymerase binding
Where does transcription termination occur?
Hairpin loops - from short inverted RNA sequences
Name the types of transcription termination
Rho-dependent
Rho-independent
What are the intrinsic terminators involved in rho-independent transcription termination and why?
8 A-T bps - following hairpin loop
Weak - RNA easily released from polymerase
What is the role of the operator within the promoter region of an operon?
Binds repressor molecule - no transcription
What is the role of the activator region of an operon, and where is it located?
Binds activator molecule - upregulates transcription
Upstream of -35 site
What does lacZ encode and what is the product’s role?
β-galactosidase - cleaves lactose into glucose and galactose
What does lacY encode and what is the product’s role?
β-galactosidase permease - pumps lactose into cell
What does lacA encode and what is the product’s role?
β-galactoside transacetylase - not needed for lactose breakdown
What is the CAP region of the lac operon?
Activator region
Binds CAP protein
