Abstract: Described are compositions and methods which allow for the efficient addition of a defined sequence at the 3'-end of a full-length cDNA in the course of first-strand cDNA synthesis from an mRNA template. A cDNA synthesis primer that is capable of annealing to mRNA is used to prime the first strand synthesis reaction. An oligonucleotide that is linked to the 5'-end of the mRNA serves as a short, extended template such that when the reverse transcriptase enzyme reaches the 5'-end of the mRNA, the enzyme switches templates and proceeds to transcribe through the end of the linked oligonucleotide. As a result, the single-stranded cDNA product which corresponds to the full-length mRNA, will have at the 3'-end a defined sequence which is complementary to the linked oligonucleotide. A conservative element in the oligonucleotide sequence responsible for this reaction can include 3 to 5 guanylic acid residues at the 3'-end of the oligonucleotide.