Ligation of foreign DNA at which of the following site will result in loss of tetracycline resistance of…
Ligation of foreign DNA at which of the following site will result in loss of tetracycline resistance of pBR322?
EcoR I
BamH I
Pst I
Pvu I
Solution
Option (2) is the answer because,
In pBR322, the restriction site for $B a m \mathrm{H} \mathrm{I}$ is present in tet $^{\mathrm{R}}$ gene. Therefore, ligation of a foreign DNA will results in loss of tetracycline resistance and recombinants will be tetracycline sensitive.
Option (1) is not the answer because, In pBR322, the restriction site of EcoR I is present outside the region of $a m p^R$ gene and tet ${ }^R$ gene.
Option (3) and (4) are not the answers because, in pBR322, the restriction sites for $P s t I$ and $P v u I$ are present in $\mathrm{amp}^{\mathrm{R}}$ gene. So, ligation of foreign DNA will result in loss of ampicillin resistance and recombinants will be ampicillin sensitive.