In a plant transformation vector, the selectable marker gene is ideally located next to the "left border" of T-DNA region, because: A. Left border…
In a plant transformation vector, the selectable marker gene is ideally located next to the "left border" of T-DNA region, because:A. Left border of T-DNA enters last into the plant cell.B. Right border of T-DNA enters last into the plant cell.C. It ensures complete transfer of T-DNA into the plant cell.Choose the most appropriate answer from the options given below:
Select an option to attempt
Correct Answer: Option C
Explanation
T-DNA border orientation and gene placement strategy:In Agrobacterium-mediated transformation, T-DNA is transferred from the right border (RB) to the left border (LB):• Transfer initiates at the RIGHT BORDER (RB) and ends at the LEFT BORDER (LB).• If T-DNA transfer is incomplete (truncated), sequences near the RB (transferred FIRST) are present; sequences near the LB (transferred LAST) may be lost.Strategic placement:• Gene of interest: placed NEAR THE RIGHT BORDER (transferred first; more likely to be delivered even in truncation events).• Selectable marker (e.g., hpt): placed NEAR THE LEFT BORDER.Rationale for question: Placing the selectable marker near the LEFT border means it is transferred LAST. In incomplete transfer events, the gene of interest (near RB) is delivered but the marker may not be, resulting in 'selectable marker-free' transgenic plants.Answer: Gene of interest near right border ensures delivery even in truncated T-DNA; marker near left border allows marker-free transgenics.