terminal transferase (terminal nucleotidyl transferase)a DNA POLYMERASE that is capable of catalysing the addition of NUCLEOTIDES to the 3′-END of a single-stranded segment of a DNA molecule. The enzyme does not require a TEMPLATE strand, unlike normal polymerases. For example, the enzyme can be used to add a tail of ADENINE residues (poly(A) tail) to the 3′ends of a cloning VECTOR and a tail of THYMINE residues (poly(T) tail) to the 3′-ends of insert DNA When mixed, the adenines will anneal to the thymines by COMPLEMENTARY BASE PAIRING to generate a recombinant vector for use in gene cloning. This method is called homopolymer tailing.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005