Properties of Yeast Episomal plasmids (YEp): Which statement correctly describes a typical YEp vector?

Introduction / Context:
Multiple classes of yeast vectors exist, each optimized for different performance characteristics. YEp vectors are designed for high-copy episomal maintenance by leveraging the endogenous 2μ plasmid system of Saccharomyces cerevisiae.

Given Data / Assumptions:

• YEp stands for Yeast Episomal plasmid.
• We compare YEp with YRp (ARS-based), YCp (CEN-based), and chromosome-like constructs (YAC).

Concept / Approach:
YEp plasmids contain the 2μ origin of replication and rep genes, enabling stable, often high-copy episomal replication in yeast. YRp vectors rely primarily on ARS elements and can be higher copy but less stable. YCp vectors carry a centromere (CEN) and are maintained at low copy with chromosome-like segregation. Telomeres are not typical for plasmids; those appear in YACs. Homologous recombination (crossing over) is a mechanism for integration, not for episomal maintenance, and is not required for YEp replication.

Step-by-Step Solution:

Verification / Alternative check:
Standard yeast molecular cloning guides describe YEps as 2μ-derived, high copy, and selectable via auxotrophic markers or drug resistance.

Why Other Options Are Wrong:

• Crossing over: pertains to integrative vectors, not episomal YEps.
• ARS-only: aligns with YRp vectors.
• CEN/TEL: belongs to YCp (CEN) or YAC (TEL).
• “Cannot replicate without integration”: false for episomal YEps.

Common Pitfalls:
Confusing ARS-only vectors with 2μ-based episomal systems; both can be high copy but have distinct backbones.

Final Answer:
Has a 2μ origin of replication and associated rep functions