Read the passage carefully and answer the given questions.
Recombinant DNA Technology
Asexual reproduction preserves the genetic information, while sexual reproduction permits variation. Traditional hybridization procedures used in plants and animals breeding very often lead to inclusion and multiplication of undesirable genes along with the desired genes. The techniques of genetic engineering, which include creation of recombinant DNA, use of gene cloning and gene transfer, overcome this limitation and allow us to isolate and introduce only one or a set of desirable genes without introducing undesirable genes into the target organism.
What is the purpose of using a gene promoter in recombinant DNA technology?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → To ensure the foreign gene expression in the host organism
A promoter is a DNA sequence placed just before a gene. RNA polymerase binds to the promoter and starts transcription from there.
Option (1) To cut DNA at specific sequences — Incorrect. Cutting DNA at a specific sequence is the work of restriction enzymes. A promoter is a stretch of DNA, not an enzyme, and it cuts nothing.
Option (2) To insert the gene into the host organism’s genome — Incorrect. The gene is carried into the host by a vector, and its ends are joined by DNA ligase. A promoter only decides whether the gene is read.
Option (3) To ensure the foreign gene expression in the host organism — Correct. The aim of most recombinant work is to get a protein. A gene that is not transcribed gives no mRNA and no protein. So the foreign gene is joined to a promoter that the host’s RNA polymerase can recognise, and the gene gets expressed.
Option (4) To replicate the gene in a bacterial cell — Incorrect. Replication of the gene depends on the origin of replication (ori) of the vector. The ori also controls how many copies are made.
Note: This passage is taken from NCERT as it is. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.