Mention the rule of (i) selectable marker, (ii) Ori and (iii) rop in E. coli cloning vector pBR322.

Explanation

(i) Selectable marker : It helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants. e.g. Ampicillin, kanamycin are considered as useful selectable markers for E.coli.
(ii) 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.
` rarr ` Responsible for controlling the copy no. of the linked DNA.
(iii) rop in E.coli cloning vector pBR322 : rop codes for the proteins involved in the replication of the plasmid.