Before You Begin
Question #47746
The Question
A biotechnology student attempts to transform plant cells using Agrobacterium tumefaciens (Method I) and E. coli cells using a recombinant pBR322 plasmid (Method II). The student mistakenly applies a 42°C heat shock during Method I, assuming it is universally required for transformation. Which of the following statements correctly highlights the fundamental difference in the DNA uptake mechanisms between these two methods?
Options
- A.
Method I relies on the active injection of T-DNA via a vir gene-mediated secretion system, whereas Method II requires thermal stress to induce transient membrane permeability.
- B.
Both methods require the creation of transient pores, but Method I uses divalent cations like Ca2+ to facilitate T-DNA entry, while Method II relies solely on a 42°C heat shock.
- C.
Method I involves the transfer of the entire Ti-plasmid into the plant nucleus without thermal stress, whereas Method II only transfers the recombinant gene of interest.
- D.
The heat shock in Method I is redundant because Agrobacterium uses its own thermal gradient to transfer DNA, whereas Method II uses heat shock to activate the origin of replication (ori).
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Divalent_Cations|Lipid_Bilayer_Fluidity|E.coli
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between biological/active horizontal gene transfer (Agrobacterium's vir system) and physical/chemical artificial transformation (heat shock).
Common Misconception: Students often conflate the steps of artificial bacterial transformation (NCERT Biotech Chapter 11) with Agrobacterium-mediated plant transformation, assuming heat shock is a universal prerequisite for all recombinant DNA uptake, or they mistakenly believe the entire Ti plasmid enters the plant cell.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Competent Cell Preparation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |