Which plasmids do not encode the information required for their own transfer to another cell (i.e., they lack the full set of conjugation genes)?

Introduction / Context:
Plasmids vary in their ability to move between cells. Conjugative plasmids carry a full set of transfer (tra) genes to build a mating apparatus. Non-conjugative plasmids lack these functions and cannot self-transfer. Recognizing this distinction is essential in molecular cloning and epidemiology of resistance genes.

Given Data / Assumptions:

• The question asks about plasmids that do not self-transfer.
• Transfer requires a functional set of tra genes and oriT.

Concept / Approach:
Non-conjugative plasmids can still sometimes be mobilized if a helper conjugative plasmid supplies missing functions in trans, but on their own they cannot initiate transfer.

Step-by-Step Solution:

Verification / Alternative check:
In lab practice, small cloning plasmids (e.g., many ColE1 derivatives) are non-conjugative unless a helper plasmid is present.

Why Other Options Are Wrong:

• Conjugative plasmids: By definition self-transfer.
• Cryptic plasmids: Often lack obvious phenotypes, but may or may not have transfer genes; the term does not strictly define transfer ability.
• None of these: Incorrect because a correct category exists.

Common Pitfalls:

• Equating “cryptic” with “non-conjugative” universally.
• Forgetting mobilization by helper plasmids does not make a plasmid conjugative.

Final Answer:
Non-conjugative plasmids