Role of non-coding RNAs

Topic: Control Of Gene Expression In Eukaryotes

The non-coding RNAs are transcribed from the DNA but are not translated into the proteins. The non-coding RNAs are the mi-RNA (micro RNA), sn RNA (small nuclear RNA), rRNA (ribosomal RNAs) and tRNAs (transfer RNA).

The micro RNA is a small RNA that does not code for proteins but is involved in the post-transcriptional regulation of gene expression and silencing of RNA. They bind with a specific untranslated region of RNA to suppress translation of the sequence.

The small nuclear RNAs are special types of RNAs that form complex with proteins to form small nuclear ribonucleoproteins. Many small nuclear ribonucleoproteins together form a molecule or an enzyme known as a spliceosome. The spliceosome helps in the processing of pre mRNA after transcription. The unwanted parts of pre mRNA known as introns are removed and the remaining parts known as exons are joined to each other by the spliceosome.

tRNA or transfer RNA helps in the transfer of amino acids to the ribosomes for the synthesis of proteins. They match the codons of the mRNA with the amino acids anticodon in the translation of the mRNA into a protein chain.

rRNA does not code for amino acids. They act as the building blocks of the ribosomes that are the factory of protein synthesis. This RNA help in reading the amino acid sequence and bind or link them to synthesize proteins.

Key Points

• micro RNA (miRNA) is involved in silencing of RNA and post-transcriptional gene regulation

• Small nuclear RNA (snRNA) binds with ribonucleoproteins to form a spliceosome. Spliceosome helps in post-transcriptional modification of pre-RNA by removing introns.

• Transfer RNA (tRNA) has anticodons for the codons of mRNA that decides which amino acid will be synthesized.

• rRNA acts as the building block of the ribosomes and also helps to read the sequence of amino acids and link them to synthesize the proteins.

Key Terms

RNA: It is a type of nucleic acid that helps in the synthesis of proteins in the cells.

Translation: It is the process of synthesis of protein from mRNA.

codon: Sequence of three nucleotides that decides which amino acid will be synthesized.

introns: Unwanted nucleotide sequences of mRNA

exons: Useful sequences of mRNA

ribonucleoproteins: any proteins that are structurally associated with nucleic acids, either DNA or RNA

spliceosome: a dynamic complex of RNA and protein subunits that removes introns from precursor mRNA

anticodon: is a trinucleotide sequence complementary to that of a corresponding codon in a messenger RNA found at one end of a transfer RNA

ribosomes: organelles made of rRNA that translates mRNA to protein chains

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