Bacterial genetics — Transformation: For gene transfer by transformation to be effective in bacteria, what must happen to the incoming DNA?

Introduction / Context:
Transformation is a mechanism of horizontal gene transfer in bacteria whereby cells take up naked DNA from the environment. For stable inheritance of new traits, the incoming DNA must avoid degradation and become part of a replicating genetic element.

Given Data / Assumptions:

• Naked DNA can enter competent bacterial cells.
• Exogenous DNA is susceptible to nucleases if not stabilized.
• Stable gene transfer requires replication and segregation during cell division.

Concept / Approach:
There are two principal routes to stability: homologous recombination into the host chromosome or establishment on a self-replicating replicon (e.g., plasmid) that carries its own origin of replication. DNA that remains free and unintegrated is rapidly degraded and not inherited by daughter cells.

Step-by-Step Solution:

Verification / Alternative check:
Classical experiments show that only transformants with chromosomal integration or plasmid establishment retain the new phenotype upon subculture, confirming the requirement.

Why Other Options Are Wrong:

• Viral genome incorporation describes transduction, not transformation.
• Free cytoplasmic DNA is unstable and not replicated.
• “None” is incorrect given established mechanisms.

Common Pitfalls:
Overlooking plasmid replication as an alternative to chromosomal integration; both confer stability if the origin is recognized by the host.

Final Answer:
It must be incorporated into the bacterial chromosome (or a replicon) to be maintained