Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
Direct DNA transfer method(s) used for plant genetic engineering is(are)
Options:
(A) microparticle bombardment
(B) electroporation
(C) polyethylene glycol treatment
(D) Agrobacterium-mediated transformation
Official Answer Key:
A;B;C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2023 Q.44)**
**1. Governing Concept**:
- **Topic**: Plant Genetic Engineering & Direct (Vector-Less) Gene Transfer
- Gene transfer methods into plant cells fall into two broad classes:
1. **Direct (Physical/Chemical / Non-Biological) Methods**:
- **Microprojectile Bombardment (Biolistics / Particle Gun)**: Gold or tungsten microcarriers coated with DNA accelerated by helium pressure.
- **Electroporation**: High-voltage electrical pulses creating transient nanometer pores in plasma membranes.
- **PEG-mediated Transformation**: Chemical induction of DNA uptake into isolated protoplasts.
- **Microinjection**: Direct glass capillary injection of DNA into nuclei.
2. **Indirect (Biological / Vector-Mediated) Methods**:
- *Agrobacterium tumefaciens* (T-DNA transfer via vir machinery) and *Agrobacterium rhizogenes*.
**2. Option Analysis**:
- **Option (A) [Biolistics (Particle bombardment)] is CORRECT**: Physical direct gene transfer utilizing accelerated microprojectiles.
- **Option (B) [Electroporation] is CORRECT**: Direct physical method using electrical field pulses to facilitate plasmid uptake into protoplasts or cells.
- **Option (C) [PEG-mediated transformation] is CORRECT**: Direct chemical transformation technique for protoplast DNA internalization.
- **Option (D) [Agrobacterium-mediated transformation] is INCORRECT**: An indirect, vector-mediated biological delivery system.
**3. Final Answer**:
- **Correct Options**: **A, B, C**
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