Method of characterizing a target ribonucleic acid (RNA) comprising forming a complementary polynucleotide which moves through a transmembrane pore

A method of characterising a target ribonucleic acid (RNA) comprising a poly A tail, the method comprising:

• (a) forming a complementary polynucleotide from the target RNA by hybridising a primer to the poly A tail of the target RNA and using the primer to reverse transcribe the target RNA to form the complementary polynucleotide, wherein the primer comprises a leader sequence and/or a region to which a polynucleotide binding protein is capable of binding;
• (b) contacting the complementary polynucleotide with a transmembrane pore such that the complementary polynucleotide moves through the pore;
• and
• (c) taking one or more measurements as the complementary polynucleotide moves with respect to the pore wherein the measurements are indicative of one or more characteristics of the complementary polynucleotide and thereby characterising the target RNA,
• wherein the method does not comprise polymerase chain reaction (PCR) or reverse transcription PCR (RT-PCR), and
• wherein the complementary polynucleotide is contacted with the pore when the complementary polynucleotide is fully or partially hybridized to the targt RNA.