Origin of Replication & Copy Number — NEET Biology
✅ Asked in NEET 2025Origin 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.
NTA tests whether students understand that ori (origin of replication) has TWO key functions: it marks WHERE replication begins AND controls HOW MANY copies of DNA are made inside host cells. The common mistake is thinking ori only marks the starting point—students forget it also regulates copy number. To score: remember that high copy number ori = many DNA copies (useful for cloning target genes), while low copy number ori = fewer copies. NTA may ask which vector to choose for maximum target DNA recovery—the answer depends on ori type, not just the vector itself.
This paragraph was tested 4 times in NEET.
Which of the following is not a function of the origin of replication (ori) in a cloning vector? (NEET 2025)
The following diagram shows restriction sites in E. coli cloning vector pBR322. What is the role of ‘X’ and ‘Y’ genes? (NEET 2024)
In a chromosome, there is a specific DNA sequence responsible for initiating replication. It is called: (NEET 2024)
The sequence that controls the copy number of the linked DNA in the vector is termed: (NEET 2020)
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