Yeast expression systems — commonly used S. cerevisiae promoters Which promoters are widely used to drive gene expression in Saccharomyces cerevisiae laboratory constructs?

Introduction / Context:
Promoter choice is central to designing yeast expression systems for basic research and biotechnology. S. cerevisiae provides strong constitutive and inducible promoters that control timing and strength of transcription. This question checks recognition of three classic workhorse promoters.

Given Data / Assumptions:

• Organism: Saccharomyces cerevisiae.
• Goal: high, regulated, or condition-specific expression.
• Promoters listed are standard in yeast cloning vectors.

Concept / Approach:
GAL1 is an inducible promoter activated by galactose and repressed by glucose, ideal for controlled induction. ADH2 is repressed by glucose (derepressed during growth on non-fermentable carbon sources), enabling metabolic state-dependent expression. PGK is a strong constitutive promoter driving robust expression during glycolysis. Together, they represent the spectrum of inducible and constitutive control used in yeast work.

Step-by-Step Solution:

Verification / Alternative check:
Yeast toolkits and commercial vectors frequently include GAL1, PGK, and ADH family promoters for modular cloning and expression studies.

Why Other Options Are Wrong:

• A single promoter choice ignores the others, all of which are widely used.
• None of the above is incorrect given extensive literature use of all three.

Common Pitfalls:
Confusing ADH1 (often stronger constitutive) with ADH2 (glucose-repressible); both ADH promoters are common in yeast vectors but have different regulation.

Final Answer:
All of the above