Vectors, Promoters, and Expression Control
Controlling Expression
Expression design
A successful construct does more than carry DNA; it controls when, where, and how strongly a gene is expressed. Researchers tune expression with promoters, enhancers, terminators, signal peptides, and copy number.
Regulatory parts
| Element | Main effect |
|---|---|
| Promoter | Sets transcription initiation and strength |
| Enhancer | Boosts transcription in certain contexts |
| Terminator | Stops transcription and helps RNA processing |
| Ribosome binding site or Kozak context | Affects translation efficiency |
| Selectable marker | Helps identify cells carrying the construct |
A strong promoter will generally cause:
Promoter strength influences how often transcription begins.
Correct answer: Higher transcription
Why might a scientist choose a tissue-specific promoter?
This helps reduce unwanted effects in other tissues.
Correct answer: To restrict expression to particular cell types
Which feature is most directly useful for identifying cells that received a construct?
Selectable markers help enrich for successfully modified cells.
Correct answer: Selectable marker
Dose matters
Too little expression may give no phenotype, while too much can stress cells or create misleading results.
Common promoter types
Constitutive promoter
- Active in many cells
- Useful for continuous expression
Inducible promoter
- Turned on by a signal
- Useful when expression could be toxic
What is one reason to use an inducible system?
Temporal control helps study essential or toxic genes.
Correct answer: To control expression at a chosen time