Recombinant DNA technology
Read the following passage carefully and answer the given questions
Biotechnology has been used by humans since times immemorial in the form of unmodified microbe mediated processes. However, rDNA technology uses genetically modified organisms and employs number of tools. The key tools are restriction enzymes, polymerase enzymes, ligases, vectors and the host organism. Restriction enzymes are also called as nucleases as they cut the DNA. Exonucleases cuts the DNA from the ends whereas endonucleases cuts the DNA at specific positions within the DNA. Endonucleases recognize a sequence of six base pairs called ‘recognition sequence’. Restriction enzymes cut both foreign DNA and vector DNA at specific point. Plasmids and bacteriophages are the commonly used vectors for transferring rDNA into the host organism. Vectors used now a days are engineered in such a way that help in easy linking with foreign DNA as well as selection of recombinants from non-recombinants. Maintenance of introduced DNA in the host and transfer of DNA to its progeny is one of the basic step of biotechnology.
rDNA is directly injected into the nucleus of an animal cell by:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Micro-injection
Recombinant DNA can be put into a host cell by several methods.
(1) Biolistics — Incorrect. In this “gene gun” method, plant cells are bombarded with fast micro-particles of gold or tungsten coated with DNA.
(2) Disarmed pathogen — Incorrect. A disarmed pathogen is used as a vector. It infects the cell and carries the recombinant DNA into it.
(3) Plasmid — Incorrect. A plasmid is a vector that carries the DNA. It is not a method of injecting DNA into a nucleus.
(4) Micro-injection — Correct. The recombinant DNA is injected directly into the nucleus of an animal cell.
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 22-05-2026 (Slot 1), and in CUET (UG) 2025 on 13-05-2025 (Slot 2).
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. 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 biolistics or gene gun. And the last method uses ‘disarmed pathogen’ vectors, which when allowed to infect the cell, transfer the recombinant DNA into the host.”