Regulation of Gene Expression: every key term you need (+ practice quiz)
25 flashcard terms for Genetics Topic 6, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 8-question quiz — free, no account needed.
Steady expression regardless of conditions, characteristic of genes whose products are always required.
Inducible operon
A cluster normally off that switches on when its substrate appears, the efficient arrangement for a catabolic pathway.
Repressible operon
A cluster normally on that switches off when its product accumulates, the efficient arrangement for a biosynthetic pathway.
Operator
A short sequence overlapping or adjacent to a promoter where a repressor binds to block transcription.
Repressor protein
A regulator that blocks transcription until a small molecule changes its shape, converting a metabolic signal into a change in binding.
Inducer
A small molecule that binds a repressor and lowers its affinity for the operator, allowing transcription to begin.
Corepressor
A small molecule that a repressor requires in order to bind the operator, so accumulation of the pathway product shuts the pathway down.
Positive control
Regulation by an activator that increases transcription, in contrast to negative control which works by relieving or imposing a block.
Catabolite repression
A preferred carbon source lowers a signalling molecule, so an activator cannot bind and alternative pathways stay off until the preferred source runs out.
Attenuation
Regulation during transcription, in which alternative folding of the new transcript decides whether the polymerase terminates early.
Riboswitch
A structured region of a transcript that binds a metabolite directly and changes shape, regulating expression without any protein regulator.
Cis-acting element
A sequence that affects only the molecule it sits on, such as a promoter or operator, so its defects cannot be rescued by a second copy elsewhere.
Trans-acting factor
A diffusible product that can act on any copy in the cell, so a working copy elsewhere in the genome can compensate for a defective one.
Transcription factor domains
Regulators typically carry separate regions for binding sequence and for activating transcription, which is why the two functions can be swapped independently.
Mediator complex
A bridging complex that transmits signals from distant regulators to the polymerase assembled at the promoter.
Combinatorial control
A gene's output is set by the combination of regulators present rather than by any single one, which is how a limited set of factors specifies many cell types.
Histone modification
Chemical marks on histone tails that loosen or tighten packing and recruit reader proteins, tuning accessibility without changing sequence.
DNA methylation
Addition of methyl groups, typically at cytosines in promoter regions, which is associated with stable silencing and is copied to daughter cells.
Expression from only the maternal or only the paternal copy, set by marks laid down in the germ line and maintained through development.
Epigenetic inheritance
Transmission of expression states through cell division without sequence change, which explains stable cell identity and some parent-of-origin effects.
MicroRNA regulation
Short transcripts guide a silencing complex to partly matching messages, blocking translation or triggering degradation.
RNA interference
Double-stranded triggers are processed into short guides that silence matching transcripts, a natural defence widely used as a laboratory tool.
Translational control
Regulation of how efficiently an existing transcript is translated, which changes protein output faster than altering transcription.
Protein stability control
Targeted degradation sets protein lifetime, so tagging for destruction can shut off activity even while transcription continues.
Feedback in regulatory networks
Negative feedback stabilizes output while positive feedback creates switch-like, self-sustaining states that lock in a developmental decision.