You can add a A-tail to a piece of DNA using a non-proof reading polymerase used in normal PCR. Just take you product, set up a normal PCR reaction but without primers, and instead of dNTPs, just add dATP. They incubate it at 72deg C for 20 mins, and you'll have A-tailed product ready for T/A cloning.

Agreed! I use the same. Good luck.

OK. In fact, I have a "Terminal Transferase enzyme". I thought about trying it with dATPs. But, as you say, it is possible to add by Itaq polymerase. So, I want to know what are the other alternatives (or enzymes) used for that aim.

Thanks a lot your support.... I will do it as you explained....

You can use "Polynucleotide kinase" for add A tail.