If a scientist wants to recover many copies of the target DNA through recombinant DNA technology, what augmentation need to be done in cloning vector?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → add origin of replication (ori) that support high copy number
The origin of replication (ori) is the sequence where copying of the vector starts. It also controls the copy number of the linked DNA.
Option (1) Reduce cloning sites — Incorrect. The number of cloning sites decides where DNA can be inserted, not how many copies are made.
Option (2) add origin of replication (ori) that support high copy number — Correct. Copy number is set by the ori, so the change needed is a vector whose ori supports a high copy number. Cloning sites and selectable markers do not change how many copies are made.
Option (3) add more selectable marker — Incorrect. A selectable marker helps pick out transformants; it does not multiply the DNA.
Option (4) add more cloning sites — Incorrect. A vector needs very few, preferably single, sites for each enzyme; more sites would cut it into pieces.
NCERT Extract:
Cloning Vectors – “… (i) Origin of replication (ori) : This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA. So, if one wants to recover many copies of the target DNA it should be cloned in a vector whose origin support high copy number.”