Which sequence in a vector is responsible for starting DNA replication and controlling the copy number of linked DNA?

Origin of replication (ori)

The correct answer is Option (3): Origin of replication (ori)

The origin of replication (ori) is the sequence in a vector that is responsible for starting DNA replication and controlling the copy number of linked DNA.This sequence is essential for the vector to be able to replicate within the host cells independently of the chromosomal DNA.

The ori ensures that once the vector is introduced into the host cell, it can be duplicated along with the host DNA during cell division, leading to the generation of multiple copies of the vector and the inserted DNA fragment.

The copy number of the linked DNA depends on the efficiency of replication from the ori site, and vectors with origins that support high copy numbers are preferred for obtaining a large amount of the target DNA.