Read the following passage carefully and answer the given questions.
DNA recombinant technology involves the use of restriction endonucleases. After having cloned the gene of interest and having optimised the conditions to induce the expression of the target protein, one has to consider producing it on a large scale. The cells harbouring cloned genes of interest may be grown on a small scale in the laboratory. In order to link the alien DNA, the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes. Presence of more than one recognition sites within the vector will generate several fragments, which will complicate the gene cloning. In Biolistics or gene gun method cells are bombarded with high velocity micro particles of gold or tungsten coated with DNA. The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. For example, you can ligate a foreign DNA at the BamHI site of tetracycline resistance gene in the vector pBR322. Since the DNA is enclosed within the membranes, we have to break the cell open to release DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids. The RNA can be removed by treatment with ribonuclease whereas proteins can be removed by treatment with protease. Other molecules can be removed by appropriate treatments and purified DNA ultimately precipitates out after the addition of chilled ethanol.
Which one of the following statements is correct with reference to biolistics?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Particles are coated with DNA
In biolistics (gene gun), plant cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA, which carry the DNA into the cells.
Option (1) Bombarding of cells with macro particles — Incorrect. The particles are micro-particles, small enough to enter a cell.
Option (2) Velocity of particles to be kept low — Incorrect. The particles are fired at high velocity to pierce the cell wall.
Option (3) Particles are coated with DNA — Correct. In biolistics (gene gun), cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA. It is a method suitable for plants.
Option (4) Zinc and nickel particles are used — Incorrect. The particles used in biolistics are of gold or tungsten, heavy metals that can be fired fast into the cells. Zinc and nickel are not used.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.