Biolistic method
Definition:
The biolistic method (also called gene gun or particle bombardment) is a physical method of gene transfer in which DNA-coated microscopic particles (usually gold or tungsten) are physically accelerated to penetrate plant, animal, or microbial cells, delivering foreign DNA directly into the cytoplasm or nucleus.
Key Concept: The method physically delivers DNA, bypassing cell wall or membrane barriers, without the need for chemical or biological carriers.
1. Principle
Microscopic metal particles (gold or tungsten) are coated with DNA or RNA.
Particles are accelerated at high speed using a gene gun or helium pressure system.
DNA enters the cell or organelle (nucleus, chloroplast, mitochondria).
Cells repair the damage and may integrate the DNA into their genome, expressing the introduced gene.
Advantages of Principle:
Works with cells with rigid walls, like plant cells.
Can target organelles, such as chloroplasts or mitochondria.
Useful for species resistant to Agrobacterium-mediated transformation.
2. Materials Required
Microscopic metal particles – tungsten (1–1.6 µm) or gold (0.6–1 µm).
Plasmid DNA – carrying gene of interest and selectable markers.
Gene gun/biolistic device – particle acceleration system using helium or high-pressure gas.
Microcarrier sheets or macrocarriers – to hold DNA-coated particles.
Target cells or tissue – plant explants, embryos, leaves, or cultured cells.
Culture media – for cell recovery and selection after bombardment.
3. Procedure / Steps
Preparation of DNA-coated particles:
Suspend gold or tungsten particles in water or ethanol.
Mix with plasmid DNA.
Precipitate DNA onto particles using calcium chloride (CaCl₂) and spermidine.
Wash and dry particles.
Loading the Gene Gun:
Place DNA-coated particles onto macrocarriers.
Assemble the gene gun apparatus with rupture discs or helium pressure system.
Bombardment / Delivery:
Target tissue (callus, leaves, embryos) is placed at appropriate distance.
High-speed particles are fired into cells.
DNA is delivered into cytoplasm and sometimes nucleus or organelles.
Recovery and Selection:
Bombarded tissue is cultured on regeneration medium.
Apply selective pressure (antibiotic, herbicide) to identify transformed cells.
Cells may develop into transgenic plants or regenerated cell lines.
4. Factors Affecting Efficiency
Factor
Effect
Particle type
Gold is less toxic than tungsten
Particle size
Smaller particles penetrate more easily; 0.6–1.6 µm
DNA loading
Higher DNA per particle → higher efficiency
Helium pressure
Too high → tissue damage; too low → low delivery
Distance between particle source and tissue
Determines penetration depth
Tissue type and age
Young, actively dividing tissue is better
Number of bombardments
Multiple shots can increase transformation but may damage tissue
5. Advantages
Direct delivery into cells with rigid walls (plants).
Can target organelles for organelle-specific transformation.
Works on species resistant to Agrobacterium-mediated transformation.
Can introduce large DNA fragments (>100 kb).
Does not require chemical reagents or viral vectors.
6. Limitations
Requires expensive equipment (gene gun).
Can cause tissue damage at high pressures.
Transformation efficiency is generally lower than Agrobacterium-mediated methods.
DNA integration is often random, not site-specific.
Only small areas of tissue can be targeted at a time.
7. Applications
Plant genetic engineering – e.g., rice, maize, wheat, tobacco.
Organellar transformation – chloroplast and mitochondrial genes.
Transgenic animal studies – embryos can be targeted in some cases.
Functional genomics – gene expression studies in cells or tissues.
Introduction of selectable markers – herbicide resistance, antibiotic resistance genes.
8. Notes / Tips
Gold particles are preferred for minimal cytotoxicity.
DNA coating must be uniform for consistent delivery.
Explants should be actively dividing to improve integration.
Multiple bombardments may increase success but risk tissue damage.
Post-bombardment culture conditions are critical for regeneration.
50 MCQs on Biolistic Method with Answers
Principle & Basics
Biolistic method is also called:
A) Gene gun
B) Electroporation
C) Microinjection
D) PEG-mediated transfer
Answer: A
Biolistic method is classified as:
A) Chemical method
B) Physical method
C) Biological method
D) Vector-mediated method
Answer: B
DNA is delivered into cells by:
A) Virus
B) Microparticles
C) Chemical reagents
D) Electroporation only
Answer: B
Metal particles commonly used are:
A) Copper and silver
B) Gold and tungsten
C) Iron and aluminum
D) Platinum and nickel
Answer: B
The primary purpose of biolistic method is:
A) DNA delivery into cells
B) Cell wall digestion
C) RNA degradation
D) Protein purification
Answer: A
DNA is coated on metal particles using:
A) Calcium chloride and spermidine
B) PEG
C) Electroporation buffer
D) Heat shock
Answer: A
Gold is preferred over tungsten because:
A) Heavier
B) Less toxic
C) Easier to accelerate
D) Cheaper
Answer: B
Particle size used is usually:
A) 0.1–0.5 µm
B) 0.6–1.6 µm
C) 2–5 µm
D) 5–10 µm
Answer: B
Particle acceleration is achieved using:
A) Helium pressure
B) Electric pulse
C) Magnetic field
D) Centrifugal force
Answer: A
Target tissue can be:
A) Plant leaves
B) Callus or embryos
C) Cultured cells
D) All of the above
Answer: D
Procedure / Steps
First step in biolistics is:
A) DNA isolation
B) DNA coating on particles
C) Tissue culture
D) Selection of cells
Answer: B
DNA-coated particles are fired to:
A) Penetrate cell wall/membrane
B) Digest DNA
C) Fuse with membrane
D) Induce mutation only
Answer: A
After bombardment, tissue is:
A) Discarded
B) Cultured for recovery and selection
C) Exposed to more particles immediately
D) Frozen
Answer: B
Selectable markers include:
A) Herbicide resistance
B) Antibiotic resistance
C) Reporter genes
D) All of the above
Answer: D
DNA integration is usually:
A) Random
B) Site-specific
C) Only in chloroplast
D) Only in mitochondria
Answer: A
Optimal tissue for bombardment is:
A) Old tissue
B) Young, actively dividing tissue
C) Dead tissue
D) Senescent tissue
Answer: B
Multiple bombardments:
A) Increase efficiency but may damage tissue
B) Always increase efficiency without damage
C) Reduce transformation
D) Have no effect
Answer: A
DNA-coated particles should be:
A) Uniformly coated
B) Coated partially
C) Not coated
D) Dissolved
Answer: A
DNA delivery can target:
A) Cytoplasm
B) Nucleus
C) Organelles
D) All of the above
Answer: D
Tissue regeneration post-bombardment requires:
A) Growth medium and selective pressure
B) Only buffer
C) Immediate freezing
D) None
Answer: A
Factors Affecting Efficiency
Helium pressure affects:
A) Particle velocity
B) Tissue penetration
C) Tissue damage
D) All of the above
Answer: D
Particle size affects:
A) Penetration efficiency
B) Cytotoxicity
C) Both A and B
D) None
Answer: C
DNA loading affects:
A) Transformation efficiency
B) Toxicity
C) Both A and B
D) None
Answer: C
Distance from gun to tissue affects:
A) Penetration depth
B) DNA uptake
C) Tissue damage
D) All of the above
Answer: D
Tissue type affects:
A) Transformation efficiency
B) Cell survival
C) Both A and B
D) None
Answer: C
Gold particles are preferred because they:
A) Penetrate deeper
B) Reduce toxicity
C) Improve DNA stability
D) All of the above
Answer: D
High particle density may:
A) Increase DNA delivery
B) Cause tissue damage
C) Both A and B
D) None
Answer: C
Precipitation reagents are used to:
A) Bind DNA to particles
B) Protect DNA
C) Both A and B
D) None
Answer: C
Young explants are better because:
A) Divide actively
B) Integrate DNA efficiently
C) Survive bombardment better
D) All of the above
Answer: D
Repeated bombardments:
A) Always improve transformation
B) Must be optimized
C) Are unnecessary
D) Only used in bacteria
Answer: B
Applications
Biolistic method is used for:
A) Plant genetic engineering
B) Animal embryo transformation
C) Organellar genome transformation
D) All of the above
Answer: D
Can target organelles like:
A) Chloroplasts
B) Mitochondria
C) Nucleus
D) All of the above
Answer: D
Advantage over Agrobacterium:
A) Works in resistant species
B) Causes fewer mutations
C) Is cheaper
D) Requires no DNA
Answer: A
Can introduce DNA fragments larger than:
A) 10 kb
B) 50 kb
C) 100 kb
D) 500 kb
Answer: C
Functional genomics uses biolistics to:
A) Study gene expression
B) Deliver reporter genes
C) Introduce RNA or protein
D) All of the above
Answer: D
Biolistics is preferred when:
A) Target cells have thick walls
B) Agrobacterium fails
C) Organellar transformation is needed
D) All of the above
Answer: D
Reporter genes used include:
A) GFP
B) GUS
C) Luciferase
D) All of the above
Answer: D
Biolistics can be combined with:
A) Selectable markers
B) Regeneration medium
C) Tissue culture techniques
D) All of the above
Answer: D
In maize and rice, biolistics is used for:
A) Herbicide resistance
B) Chloroplast transformation
C) Both A and B
D) None
Answer: C
Biolistics can deliver:
A) DNA
B) RNA
C) Proteins
D) All of the above
Answer: D
Advantages
Works on cells with rigid walls?
A) Yes
B) No
Answer: A
Direct physical delivery?
A) Yes
B) No
Answer: A
Can deliver DNA to organelles?
A) Yes
B) No
Answer: A
Requires chemical carriers?
A) No
B) Yes
Answer: A
Can introduce large DNA fragments?
A) Yes
B) No
Answer: A
Limitations
Expensive equipment required?
A) Yes
B) No
Answer: A
Can cause tissue damage?
A) Yes
B) No
Answer: A
Transformation efficiency generally:
A) Lower than Agrobacterium
B) Higher than Agrobacterium
Answer: A
DNA integration is:
A) Random
B) Site-specific
Answer: A
Biolistics is best suited for:
A) Plant tissue with thick walls
B) Bacterial plasmid transformation
C) Yeast only
D) Animal tissue only
Answer: A
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