Vector choices in cloning: Which of the following is NOT commonly used as a DNA cloning vector in standard molecular biology workflows?

Introduction / Context:
Vectors are engineered DNA molecules used to carry inserts for propagation or expression in host cells. Common vector platforms include plasmids, bacteriophages, cosmids, and artificial chromosomes (BACs/YACs), chosen based on insert size and purpose. Organisms like fungi are hosts or expression systems, not vectors themselves.

Given Data / Assumptions:

• Vectors must be DNA constructs with ori and selection markers.
• Hosts such as bacteria, yeast, or fungi replicate vectors but are not vectors.
• Cosmids and artificial chromosomes accommodate larger inserts than standard plasmids.

Concept / Approach:
Identify which choice is not a DNA construct designed for carrying foreign DNA. Plasmids, cosmids, BACs/YACs, and lambda-derived vectors are all established cloning systems. “Fungi” are organisms and therefore not vectors by definition.

Step-by-Step Solution:

Verification / Alternative check:
Consult vector maps and cloning manuals: plasmids, cosmids, and artificial chromosomes are listed as vectors; fungi are listed as hosts or expression systems.

Why Other Options Are Wrong:

• Artificial chromosome: classic large-insert vectors (BAC/YAC).
• Cosmid: plasmid–phage hybrid vector enabling larger inserts.
• Plasmid: the most common cloning vector.
• Bacteriophage lambda–based vector: widely used for genomic libraries.

Common Pitfalls:
Confusing host organisms with vector DNA; the presence of selectable markers and ori distinguishes a vector from its host.

Final Answer:
Fungi