Recombinant DNA
Read the following passage carefully and answer the given questions.
Recombinant DNA can be forced into competent cells by incubating the cells with recombinant DNA on ice, followed by heat shock and placing them back on ice. This enables the bacteria to take up the recombinant DNA. In a method known as micro-injection, recombinant DNA is directly injected into the nucleus of an animal cell. In another method, suitable for plants, cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA in a method known as gene gun and the last method uses ‘disarmed pathogen’ vectors, which when allowed to infect the cell, transfer the recombinant DNA into the host. 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. This can be achieved by treating the bacterial cells/plant or animal tissue with enzymes. 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.
Recombinant DNA is directly injected into the nucleus of an animal cell by the method of:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Micro-injection
There are different ways to put DNA into a host cell. In micro-injection, the recombinant DNA is injected with a fine needle directly into the nucleus of an animal cell.
(1) Gene gun — Incorrect. It shoots DNA-coated gold or tungsten particles into plant cells. It is the same method as biolistics.
(2) Micro-injection — Correct. It injects DNA directly into the nucleus of an animal cell.
(3) Biolistics — Incorrect. This is another name for the gene gun method, used for plants.
(4) Electron microscopy — Incorrect. This is a way to see tiny objects. It is not a way to introduce DNA.
Note 1: 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.
Note 2: A similar question was also asked in CUET (UG) 2026 on 25-05-2026 (Slot 2), in CUET (UG) 2025 on 13-05-2025 (Slot 2), and in CUET (UG) 2023 on 02-07-2023 (Slot 3).
NCERT Extract:
Cloning Vectors – “… Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 420C (heat shock), and then putting them back on ice. This enables the bacteria to take up the recombinant DNA. This is not the only way to introduce alien DNA into host cells. In a method known as micro-injection, recombinant DNA is directly injected into the nucleus of an animal cell.”