Nopaline Ti-plasmid — number of integrated T-DNA segments When integrated into the plant nuclear genome, the nopaline-type Ti-plasmid T-DNA is typically present as how many continuous T-DNA segments?

Introduction / Context:
Ti plasmids are grouped by opines synthesized in transformed tissue (e.g., nopaline, octopine, agropine). Their T-DNA organization differs, and recognizing these patterns aids vector design and interpretation of transformation outcomes.

Given Data / Assumptions:

• Nopaline-type Ti plasmids commonly have one T-DNA region.
• Octopine-type plasmids often possess two (TL and TR).
• The question targets the nopaline configuration only.

Concept / Approach:

In nopaline Ti plasmids, the T-DNA integrated into the plant genome is typically a single, continuous segment bounded by left and right border sequences. In contrast, octopine types can have two discrete T-DNA regions. Therefore, the correct choice is a single segment.

Step-by-Step Solution:

Verification / Alternative check:

Comparative Ti plasmid maps consistently depict one T-DNA in nopaline types, validating this answer.

Why Other Options Are Wrong:

Two segments describe many octopine plasmids. Three or four segments are not canonical. Tandem repeats can occur in some events, but are not the default organization implied by the question.

Common Pitfalls:

Assuming all Ti plasmids share the same dual-segment architecture; they do not.

Final Answer:

A single segment of T-DNA