Question: 146. The following diagram showing restriction sites in E.coli cloning vector pBR 322 . Find the role of ‘ X ‘ and ‘ Y ‘ genes.
(1) The gene ‘ X ‘ is responsible for resistance to antibiotics and ‘ Y ‘ for protein involved in the replication of Plasmid.
(2) The gene ‘ X ‘ is responsible for controlling the copy number of the linked DNA and ‘ Y ‘ for protein involved in the replication of Plasmid.
(3) The gene ‘ X ‘ is for protein involved in replication of Plasmid and ‘ Y ‘ for resistance to antibiotics.
(4) Gene ‘ X ‘ is responsible for recognition sites and ‘ Y ‘ is responsible for antibiotic resistance.
Answer: Option (2)
Explanation:
The plasmid pBR322 is a commonly used E.coli cloning vector that contains several important functional regions.
The region marked as ‘ X ‘ represents the
By controlling the copy number, the rop gene ensures stable maintenance of the linked foreign DNA.
The region marked as ‘ Y ‘ represents the origin of replication, also called ori.
The ori region is essential for initiating DNA replication and produces proteins involved in plasmid replication.
Therefore, ‘ X ‘ controls the copy number of linked DNA and ‘ Y ‘ is involved in plasmid replication, making option (2) correct.