Table 1

Types, size and function of RNA

Protein coding or non-codingType of RNASize (number of nucleotides)Function
CodingMessenger RNA (3%–5% of total)19 VariableTranslated into proteins by ribosomes.
structural and catalytic
Ribosomal RNA (80% of total)19 Four subunits (120, 160, 1900 and 4700 nucleotides)Facilitates mRNA translation into protein.
Transfer RNA19 80Collects amino acids and delivers to ribosome to make protein.
Non-codingSmall nuclear and small nucleolar RNA (snRNA/snoRNA)20 60–300Control mRNA and rRNA splicing.
Regulatory non codingMicroRNA (miRNA)12 19–24Regulate gene expression at a post-transcription level by translational repression or mRNA degradation.
Piwi-interacting RNA19 >23Gene silencing of transposons and repetitive sequences.
Long non-coding RNAs12 >200Many and broad functions including: gene regulation, chromosomal dynamics and telomere biology.