Abstract: Disclosed herein are methods of reverse transcribing a polynucleotide comprising an unnatural ribonucleotide comprising reverse transcribing the polynucleotide with a reverse transcriptase in the presence of an unnatural dNTP comprising an unnatural nucleobase, wherein the reverse transcriptase polymerizes cDNA into which the unnatural NTP is incorporated. In some embodiments, the polynucleotide is present at a concentration less than or equal to about 500 nM and/or the polynucleotide is a tRNA, mRNA, RNA aptamer, or a member of a plurality of RNA aptamer candidates.