Question

In pBR $322$, recognition sequences, that are present on the same type of selectable marker

• A. $BamHI,SalI$
• B. $PstI,PvuI$
• C. None of the above
• D. Both (A) and (B)

Answer 1

The correct option is D Both (A) and (B)

pBR$322$
pBR$322$ is a plasmid and was one of the first widely used Escherichia coli cloning vectors used to create recombinant DNA and obtain multiple copies of the alien gene. It is named after Bolivar and Rodriguez.

Features of pBR $322$
Common features of pBR$322$ are as follows:

• Restriction sites - It has multiple restriction sites for different restriction enzymes such as Pvu II, Pvu I, BamH I, EcoR I, Hind III, Pst I, Sal I, Cla I, etc.
• Rop - It is a specific base sequence that codes for the rop protein involved in the replication of the plasmid.
• Selectable markers - It has two selectable markers, one for ampicillin resistance ampR and one for tetracycline resistance tetR.
• Ori - It has an ori site or origin of replication site. Any piece of DNA when linked to this sequence can be made to replicate within the host cells.

Pictorial representation of pBR$322$
Pictorial representation of pBR$322$:

Selectable markers
The amp${}^R$ and tet${}^R$gene present on pBR $322$ are selectable markers as they provide ampicillin and tetracycline resistance to the host cell respectively. Therefore, host cells containing pBR$322$ can grow in nutrient media with ampicillin and tetracycline.

Restriction sites at selectable markers
The restriction sites present at the selectable marker gene region on pBR322 are as follows:

• tet${}^R$ - $BamHI$ and $SalI$
• amp${}^R$ - $PvuI$ and $Pst1$

Final answer:
c. Both (A) and (B)