Bacterial Gene Regulation
This regulatory system turns genes ON in response to the presence of a substrate.
What is an inducible operon (e.g., lac operon)?
This prokaryotic protein directs RNA polymerase to specific promoter sequences.
What is a sigma factor?
This modification protects eukaryotic mRNA from degradation and aids ribosome binding.
What is the 5′ cap?
This bacterial mRNA sequence aligns the ribosome correctly at the start codon.
What is the Shine–Dalgarno sequence?
This principle explains why proteins fold into their native conformations spontaneously.
What is minimization of Gibbs free energy?
This type of operon is usually ON but becomes OFF when its end product accumulates.
What is a repressible operon (e.g., trp operon)?
These DNA elements determine where RNA Pol II assembles in many eukaryotic genes.
What are core promoter elements (e.g., TATA box)?
This RNA feature increases transcript stability and regulates translation efficiency.
What is the poly‑A tail?
This initiation strategy replaces Shine–Dalgarno pairing in eukaryotes.
What is 5′‑cap–dependent scanning?
These proteins assist folding without becoming part of the final structure.
What are molecular chaperones?
In glucose absence, the lac operon requires this additional signal for maximal transcription.
What is CAP–cAMP positive control?
This modification increases DNA accessibility without changing the DNA sequence itself.
What is histone acetylation?
This process expands protein diversity without increasing gene number.
What is alternative splicing?
This enzyme ensures the correct amino acid is attached to the correct tRNA.
What is aminoacyl‑tRNA synthetase?
This modification can rapidly change protein activity without new synthesis.
What is post‑translational modification?
Removal of the lac repressor alone does not guarantee high transcription under all conditions because of this regulatory layer.
What is positive control by CAP–cAMP?
RNA Pol II and transcription factors can be present, yet transcription fails because this condition limits access.
What is condensed (heterochromatic) chromatin?
Gene expression is reduced without altering transcription because regulation occurs at this level.
What is post‑transcriptional regulation?
The ribosome checks codon–anticodon pairing, but amino acid identity is determined earlier by this process.
What is tRNA charging by aminoacyl‑tRNA synthetases?
Protein levels change rapidly even when mRNA levels remain constant due to regulation at this level.
What is protein stability or degradation control?
This mechanism links nutrient availability to gene expression by exploiting coupled transcription and translation.
What is attenuation in the trp operon?
Phosphorylation of this RNA Pol II region coordinates transcription with RNA processing.
What is the CTD (C‑terminal domain)?
This pathway uses small RNAs to suppress gene expression by targeting mRNA after it is made.
What is RNA interference (RNAi)?
This flexibility in base pairing reduces the number of tRNAs required without reducing accuracy.
What is wobble base pairing?
This ATP‑dependent system selectively removes damaged or regulatory proteins.
What is ubiquitin‑proteasome–mediated degradation?