The TA cloning method takes advantage of the terminal transferase activity of some DNA polymerases such as Taq polymerase. This enzyme adds a single, 3'-A overhang to each end of the PCR product. This makes it possible to clone this PCR product directly into a linearized cloning vector with single, 3'-T overhangs. DNA polymerases with proofreading activity, such as Pfu polymerase, can not be used because they provide blunt-ended PCR products.
TA cloning kits are available from different manufacturers.
We have created a circular TA cloning vector, pTA Plus, based on pPCR-Script Amp (Stratagene).
Digestion of this vector in two sequential reactions with BamH I and Xcm I gives a linearized vector with 3'-T overhangs and a low background of non-recombinants.
TOPO TA cloning
The TOPO TA cloning method combines the advantages of TA cloning with the ligation activity of topoisomerase I. This allows direct ligation of PCR products in just 5 minutes.
TOPO TA cloning kits are available from Invitrogen.