Lecture 6 - Prokaryotic Gene Regulation Flashcards
What does a gene include?
The regulatory elements that control its transcription
What is the central dogma of molecular biology (direction of information flow in cells)?
Replication, DNA, transcription, RNA, translation, protein
Transcription and translation occur only after what?
Induction
Transcription and translation is _____ in prokaryotic cells, but ____ in eukaryotic cells
coupled, separated
The pivitol point of control for gene expression in prokaryotic cells is often at the site of transcriptional initiation, which is what?
the promoter
What are the three methods to identify the sequence of a bacterial promoter?
- Sequence DNA fragments protected by RNA polymerase from digestion with deoxyribonuclease
- align sequences upstream of the initiation site of transcription
- analyze mutants with enhanced or diminished rates of transcription
What are the three stages of RNA synthesis?
Initiation, Elongation, Termination
What happens in the initiation stage of RNA synthesis?
RNA polymerase recognizes a promoter, melts the TATA box, and initiates the incorporation of the first ribonucleoside triphosphates into the nascent RNA
What happens in the elongation stage of RNA synthesis?
growth of the RNA polymer in the 5’ to 3’ direction
What happens in the termination stage of RNA synthesis?
synthesis of the RNA polymer stops at precisely defined sites coded by the DNA template
The core enzyme (RNA polymerase) consists of what?
- 2 copies of the alpha subunit
- one copy of each of the beta, beta prime and omega subunits
What is the omega subunit not essential for?
for transcription, but it helps stabilize the RNA polymerase
What is required for promoter recognition and initiation of transcription?
the holoenzyme ( 2 alpha subunits, 1 beta subunit, 1 beta prime subunit, 1 sigma subunit)
When is the sigma factor released from the holoenzyme?
after initiation, to participate in recognition of other promoters
What completes elongation and termination of the RNA transcript?
the core enzyme ( 2 alpha subunits, 1 beta subunit, 1 beta prime subunit)
What is the irreversible step in initiation of transcription transition?
going from a closed-promoter complex to a open-promoter complex
What are the two types of metabolic pathways?
- catabolic pathway: breakdown chemicals
- anabolic pathways: build up chemicals
Who discovered the regulation of the lactose operon?
Jacob and Monod
Low levels of beta-galactosidease in the bacterial cell converts lactose to what?
allolactose (an isomer of lactose), the actual inducer of the lactose operon
What does the binding of the lactose repressor protein to the operator do?
blocks the transcription of the operon
Is the conformational transition of the lactose repressor upon binding allolactose a reversible or non-reversible process?
a reversible process
Regulatory proteins undergo a conformational change upon binding to what?
- a small molecule (ligand) that decrease or increases its affinity (binding) for DNA
What are proteins that undergo a conformational change upon binding a ligand, such as repressor proteins called?
Allosteric proteins
