Given below are two statements:
Statement I: Any piece of DNA linked to the origin of replication of a vector can be made to replicate within the host cells.
Statement II: To recover many copies of the target DNA, it should be cloned in a vector whose origin supports a low copy number.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Statement I is true but Statement II is false
The origin of replication (ori) is the sequence from where replication starts. Any DNA linked to it gets copied in the host, and the ori also controls the copy number of the linked DNA. So the choice of vector decides how many copies of the target DNA we get.
Statement I: Any piece of DNA linked to the origin of replication of a vector can be made to replicate within the host cells. — True. Linking to the ori is what makes alien DNA replicate in the host.
Statement II: To recover many copies of the target DNA, it should be cloned in a vector whose origin supports a low copy number. — False. Many copies need a vector whose origin supports a high copy number.
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.”