Write down any two methods of introducing Recombinant DNA into a host cell.

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Q. Write down any two methods of introducing Recombinant DNA into a host cell.

Jammu Kashmir JkboseJKBOSE Class 12 Annual Regular Examination 2026Subjective· 3mImportance★★★★★

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Recombinant DNA can be delivered into a host cell either by physically injecting it in (micro-injection) or by physically shooting it in on tiny particles (the biolistic/gene gun method); these are two of several 'physical' methods used alongside vector-mediated transfer.

Once a gene of interest has been cloned into a suitable vector to make a recombinant DNA molecule, it must be introduced into a host cell so the host's machinery can replicate/express it. Two commonly used physical methods are:

Micro-injection: The recombinant DNA is directly injected into the nucleus of an animal cell using an extremely fine glass micropipette/needle under a microscope. This method is often used to introduce DNA into animal egg cells/embryos, e.g., to create transgenic animals.
Biolistics / Gene gun (particle bombardment) method: The recombinant DNA is coated onto the surface of high-density micro-particles of gold or tungsten, which are then physically shot ('bombarded') at high velocity into the target plant cells or tissue using a gene gun. This method is especially useful for plant cells, whose thick cell wall makes other delivery methods difficult.

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2025Set X11 markMCQ
$Q. In which method the plant cells are bombarded with high velocity microparticles of gold coated with DNA?$
(a) Microinjection
(b) Biolistics
(c) Heat shock
(d) Cloning
›Reveal solutionSolution

Bombarding plant cells with high-velocity gold/tungsten microparticles coated with DNA is the biolistics (gene gun) method.

Biolistics, also called the gene gun method, introduces alien DNA into cells (especially plant cells) by bombarding them with high-velocity microparticles of gold or tungsten coated with DNA. Microinjection directly injects DNA into a cell/nucleus using a fine needle, heat shock is used to …
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CBSE 2025Set ANNUAL1 mark
$Q. Name any two methods of vectorless gene transfer.$
›Reveal solutionSolution

Vectorless (direct) gene transfer methods introduce foreign DNA into a cell without using a biological vector such as a plasmid or virus; common examples include the gene gun and micro-injection.

In the gene gun (biolistic/particle bombardment) method, DNA is coated onto tiny gold or tungsten particles, which are then physically shot into plant cells/tissue at high velocity, allowing the DNA to enter the cell and, in some cases, integrate into the genome - this method is especially useful for plant cells with rigid cell walls.

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CBSE 2025Set ANNUAL1 mark
$Q. Name the method in which the alien DNA is directly injected into the nucleus of an animal cell.$
›Reveal solutionSolution

Micro-injection is the technique in which recombinant/alien DNA is directly injected into the nucleus of an animal cell (or into a fertilised egg/embryo) using a fine glass micropipette under a microscope.

Bacterial cells can take up foreign DNA on their own once made 'competent' (e.g. by CaCl2 treatment and heat shock), but this approach does not work for most animal cells because of their more complex membrane systems and low natural transformation efficiency. Several methods have therefore been developed to introduce alien DNA into other kinds of host cells:

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CBSE 2024Set E1 markMCQ
$Q. Which of the following methods is used to inject recombinant DNA into nucleus of animal cell directly?$
(a) Transfection
(b) Transformation
(c) Gene gun
(d) Microinjection
›Reveal solutionSolution

Microinjection injects recombinant DNA straight into the nucleus of an animal cell using a fine glass needle.

Several methods deliver foreign DNA into host cells. In animal cells, recombinant DNA can be injected directly into the nucleus using an extremely fine needle — this is called microinjection. The gene gun (biolistics) method, in contrast, is used for plant cells, where cells are bombarded with high-velocity micro-particles …

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CBSE 2020Set 57/3/11 markMCQ
$Q. Introduction of an alien DNA into a plant host cell is achieved by making them (A) Competent with bivalent ions (B) Using microinjections (C) Using gene gun (D) Using lysozymes and chitinase$
›Reveal solutionSolution
The question asks which method is used to introduce alien DNA into a plant host cell. The correct answer is the gene gun (option C), because plant cells have a tough cell wall that blocks direct entry, and the gene gun physically shoots DNA-coated particles through it.

Concept and Intuition

The core challenge here is the plant cell wall. Unlike animal cells, which have only a flexible plasma membrane, plant cells are surrounded by a rigid wall made of cellulose, hemicellulose, and pectin. This wall is a formidable physical barrier.

So, when we want to introduce foreign DNA into a plant cell, we cannot simply use the same tricks that work for bacteria or animal cells. We need a method that either:

Bypasses the wall entirely (e.g., by removing it first), or

Punches through it physically.

The gene gun (also called a biolistic particle delivery system) does exactly the latter. It fires microscopic gold or tungsten particles coated with DNA at high velocity into the plant tissue. The particles penetrate the cell wall and membrane, delivering the DNA directly inside.

Let's see why the other options fail for plant cells specifically.

Step-by-Step Breakdown

Option (A): Competent with bivalent ions

This is the standard method for making bacterial cells (like E. coli) take up plasmid DNA. Treating them with cold calcium chloride (CaCl₂) and a heat shock makes their membranes permeable.

Why it fails for plants: Plant cell walls are too thick and rigid for this chemical treatment to work. Even if the membrane becomes permeable, the DNA cannot physically reach it through the wall.

Option (B): Using microinjections

This works beautifully for animal cells (e.g., injecting DNA into a fertilized egg or a cultured cell). A fine glass needle directly delivers DNA into the nucleus or cytoplasm.

Why it fails for plants: The plant cell wall is too tough for a glass needle to penetrate without shattering the tip or crushing the cell. Also, plant cells are often part of a tissue, making individual microinjection impractical and inefficient.

Option (C): Using gene gun — This is correct. …
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Q.Write down any two methods of introducing Recombinant DNA into a host cell.

Concept understanding — Direct/Physical Methods of Gene Transfer

Direct (Physical) Methods of Gene Transfer

The Main Physical Methods

Why "Direct" Matters …

Concept and Intuition

Step-by-Step Breakdown

Q.Write down any two methods of introducing Recombinant DNA into a host cell.

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