Biology · Biotechnology: Principles and Processes · NEET
Microinjection is used for ANIMAL cells. The recombinant DNA is injected directly into the nucleus of the animal cell using a very fine needle. Animal cells have no rigid wall, so a needle can reach the nucleus. For plant cells (which have a tough cell wall), the gene gun is used instead. NEET loves to swap these two, so lock it in: needle = animal, gun = plant.
Microinjection injects DNA directly into the nucleus of a single animal cell with a needle. The gene gun (biolistics) bombards plant cells with high-velocity micro-particles of gold or tungsten that are coated with DNA. Microinjection is precise and one cell at a time; biolistics is a shotgun-style method that hits many plant cells. Different target (animal vs plant), different tool (needle vs particle bombardment).
Gold and tungsten are heavy (high density) metals, so tiny particles of them carry enough momentum to punch through the rigid plant cell wall at high speed. They are also chemically inert (unreactive), so they do not harm the cell or the DNA. The DNA is simply coated on the outside of these micro-particles and carried in. NCERT names exactly these two metals, so remember 'gold or tungsten'.
Yes, biolistics and gene gun are the SAME method. The word comes from 'biological ballistics' (shooting particles). Cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA. So if a NEET option says 'biolistics' and another says 'gene gun', they are describing one technique, not two.
NCERT lists four methods total. (1) Making cells competent using a divalent cation like calcium (CaCl2) plus a brief heat shock, so bacteria take up DNA. (2) Microinjection into animal cell nuclei. (3) Biolistics/gene gun for plant cells. (4) 'Disarmed pathogen' vectors (like disarmed Agrobacterium for plants or disarmed retroviruses for animal cells) that infect the cell and deliver the DNA. All four aim to get recombinant DNA inside the host.
Match List-I with List-II. (A) Kanamycin (B) ClaI (C) Disarmed retroviruses (D) Kanamycin R gene | (I) Delivers genes into animal cells (II) Selectable marker (III) Restriction site (IV) Antibiotic resistance
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Microinjection, where recombinant DNA is injected directly into the nucleus of an animal cell using a fine needle. Disarmed retroviruses can also deliver genes into animal cells.
Gold or tungsten. Both are dense enough to carry DNA through the plant cell wall at high velocity and are inert, so they do not damage the cell or DNA.
No. Bacteria are made 'competent' using a divalent cation (like calcium) and a brief heat shock. The gene gun (biolistics) is used mainly for plant cells.
A pathogen whose disease-causing genes are removed, so it can still infect a cell and deliver the recombinant DNA but cannot cause disease. Examples: disarmed Agrobacterium for plants, disarmed retroviruses for animal cells.
The cell membrane and (in plants) the rigid cell wall are hydrophobic barriers that block large charged DNA molecules. So special methods like competence treatment, microinjection, biolistics, or vectors are needed to get DNA inside.
