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Ligation of foreign DNA at which of the following site will result in loss of tetracycline resistance of pBR322?
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Verified Answer
The correct answer is:
BamH I
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.
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.
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