RNA, like DNA, is a heteropolymer of mononucleotides connected by phosphodiester bond. However, RNA mononucleotide has ribose instead of deoxyribose and Uracil instead of Thymine. Moreover, cellular RNAs are predominantly single stranded, but can form intramolecular hydrogen bonds in DNA-like (Watson-Crick pattern) or other patterns such as Hoogstein base pairing.
RNAs, unlike DNA form a variety of secondary and tertiary structures.
Three main classes of RNA incude:
- messenger RNA (mRNA): serve as a template for protein synthesis
- non-coding RNA (ncRNA): serve diverse functions ranging from being a part of core-protein synthesis machinery to gene regulation
- genomic RNA: serve as genetic material of certain viruses
ncRNA is a diverse class including:
- Ribosomal RNAs (rRNA): structural and catalytic components of protein synthesis
- Transfer RNA (tRNA): carry charged amino-acids for protein synthesis]
- Long-noncoding RNA: diverse functions (yet to be characterized)
- MicroRNA (miRNA): small regulatory RNA which post transcriptionally regulate gene expression
- Small interfering RNA (siRNA) :small RNAs which silence target mRNA/lncRNA
- Piwi-associated RNA (piRNA): small RNAs that silence transposons