Provided is a polynucleotide comprising mRNA, rRNA or viral RNA, comprising ribose rings that are covalently modified at the 2'-OH position. Further provided are methods for producing a double-stranded oligo- or polynucleotide from a template comprising an oligo- or polyribonucleotide, a proportion of the ribose rings of which are covalently modified at the 2'-OH position to bear a substituent which enables replication of the template by the nucleic acid polymerase. Also provided is use of a poly-nucleotide comprising mRNA, rRNA or viral RNA, a proportion of the ribose rings of which are covalently modified at the 2'-OH position, in a hybridisation reaction