Q.36 The following chemical compound is used in gene transfer using physical delivery methods:
1. Paradichlorobenzene
2. Polyethylene glycol
3. Chloramphenicol
4. Colchicine
Gene Transfer Biocatalyst: Polyethylene Glycol Role Explained
Polyethylene glycol (PEG) facilitates DNA uptake in physical gene transfer methods by altering cell membrane permeability. The correct answer is option 2: Polyethylene glycol.
Correct Answer
Option 2: Polyethylene glycol.
PEG mediates direct DNA uptake into protoplasts or cells by inducing transient membrane pores, often combined with divalent cations. Widely used in plant and yeast transformation, it enables chemical-physical hybrid delivery without electroporation or guns.
Option Analysis
Option 1: Paradichlorobenzene
A volatile fumigant used as insecticide or deodorant, with no role in gene transfer. It disrupts insect nervous systems but lacks membrane-altering properties for DNA delivery.
Option 2: Polyethylene Glycol (Correct)
PEG (15-20%) mixes with protoplasts and DNA, promoting endocytosis or fusion for foreign DNA entry. Common in protocols like yeast and plant cell transformations.
Option 3: Chloramphenicol
An antibiotic inhibiting bacterial protein synthesis by binding 50S ribosomal subunit. Used for selection post-transformation, not for DNA delivery itself.
Option 4: Colchicine
A microtubule-depolymerizing alkaloid used for polyploidy induction in plants. It blocks spindle formation but does not facilitate gene transfer.
| Option | Compound | Used in Gene Transfer? | Reason |
|---|---|---|---|
| 1 | Paradichlorobenzene | No | Insecticide |
| 2 | Polyethylene glycol | Yes | Membrane permeabilization |
| 3 | Chloramphenicol | No | Antibiotic selection |
| 4 | Colchicine | No | Mitotic inhibitor |
Exam Insights
PEG distinguishes chemical-physical gene transfer from pure physical (electroporation, biolistics). Key for biotech questions on transformation methods.
