Question

A transgenic event is differentiated from other events by

• A. Copy number
• B. Site of integration
• C. Both copy number and site of integration
• D. Type of protein produced

Hint:

Independent transgenic lines (events) are characterized and patented based on:
1. The unique chromosomal location (site of integration).
2. The number of transgene inserts (copy number).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
In plant transformation, a "transgenic event" refers to a unique instance of transgene integration into the host genome.
When plant tissues are transformed, different cells take up the foreign DNA independently, resulting in distinct transgenic lines or "events."

Step 2: Detailed Explanation:
Each independent transgenic plant line derived from a transformation experiment represents a unique event, characterized by:
1. Site of integration: The transgene integrates randomly into the host plant's chromosomes.
Because the integration site varies between events, the transgene may land in a transcriptionally active euchromatin region or an inactive heterochromatin region, which can lead to differences in transgene expression (due to position effects).
2. Copy number: Different events can integrate varying numbers of copies of the transgene cassette (ranging from a single copy to multiple tandem or rearranged copies).
High copy numbers can sometimes trigger gene silencing mechanisms (such as RNA interference), reducing expression levels.
While different events of the same construct produce the same type of protein, they differ in their integration site and copy number.
These molecular features are analyzed using Southern blotting and sequencing to characterize and differentiate transgenic events for commercial release.

Step 3: Final Answer:
A transgenic event is differentiated from others by both its copy number and site of integration, which corresponds to Option (C).