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Question:

A foreign DNA and plasmid cut by the same restriction endonuclease can be joined to form a recombinant plasmid using Polymerase III, Eco RI, Ligase, or Taq polymerase?

Ligase

Polymerase III

Taq polymerase

Eco RI

Solution:

Polymerase III and Taq polymerase are enzymes of DNA polymerization and add deoxyribonucleotides to the primer in 5' to 3' direction. EcoRI is a restriction enzyme from E. coli that digests DNA at G^AATTC sites. DNA ligase enzyme joins two DNA fragments together via a phosphodiester bond between the 3’ hydroxyl at the end of one fragment and a 5’ phosphate at the end of another fragment. Foreign DNA and a plasmid having complementary ends can be ligated using DNA ligase. Therefore, the correct answer is option B.