A lab technique where a nucleic acid homopolymer (a long chain of the same nucleotide over and over) is attached to the end of a piece of DNA as a part of DNA cloning. It is especially useful in cDNA cloning to get the cDNA inserted into the cloning vector -- a nucleic acid homopolymer which contains the complementary nucleotide to the cDNA tail is attached to the vector, which then pairs with the tail on the cDNA.