Only a small proportion of the genome codes for proteins, but much of the rest is transcribed into RNA. Non-coding RNA (ncRNA) is RNA that is not translated into protein. Instead, the RNA molecule itself has a function.ncRNA involved in protein synthesis
• Transfer RNA (tRNA) carries specific amino acids to the ribosome and pairs its anticodon with codons on mRNA.
• Ribosomal RNA (rRNA) makes up much of the ribosome, together with proteins, and catalyses the formation of peptide bonds.
• Small RNAs in spliceosomes recognise the boundaries of introns during RNA splicing.ncRNA that regulates gene expression
• MicroRNA (miRNA): short RNA molecules, about 22 nucleotides long, coded for by the cell's own genes. They bind to complementary sequences in target mRNAs, reducing their translation or causing them to be broken down. One miRNA can regulate many different mRNAs.
• Small interfering RNA (siRNA): short double-stranded RNA that silences genes by causing specific mRNAs to be broken down.
• Long non-coding RNA (lncRNA): longer than 200 nucleotides. Some attract enzymes that modify chromatin. For example, the lncRNA called Xist coats one of the two X chromosomes in female mammals and causes it to be condensed and inactivated.Why ncRNA matters
Non-coding RNAs can switch genes on or off quickly and precisely, and they help control differentiation and development. Faults in ncRNAs have been linked to diseases including some cancers.
• Transfer RNA (tRNA) carries specific amino acids to the ribosome and pairs its anticodon with codons on mRNA.
• Ribosomal RNA (rRNA) makes up much of the ribosome, together with proteins, and catalyses the formation of peptide bonds.
• Small RNAs in spliceosomes recognise the boundaries of introns during RNA splicing.ncRNA that regulates gene expression
• MicroRNA (miRNA): short RNA molecules, about 22 nucleotides long, coded for by the cell's own genes. They bind to complementary sequences in target mRNAs, reducing their translation or causing them to be broken down. One miRNA can regulate many different mRNAs.
• Small interfering RNA (siRNA): short double-stranded RNA that silences genes by causing specific mRNAs to be broken down.
• Long non-coding RNA (lncRNA): longer than 200 nucleotides. Some attract enzymes that modify chromatin. For example, the lncRNA called Xist coats one of the two X chromosomes in female mammals and causes it to be condensed and inactivated.Why ncRNA matters
Non-coding RNAs can switch genes on or off quickly and precisely, and they help control differentiation and development. Faults in ncRNAs have been linked to diseases including some cancers.