RNA, or ribonucleic acid, is a polymer composed of ribose sugars, phosphate groups and the bases adenine, guanine, cytosine and uracil. It plays central roles in gene expression and regulation.
Explanation
Compared with DNA, RNA is usually single‑stranded and contains the sugar ribose instead of deoxyribose and uracil in place of thymine. This structural flexibility allows RNA to fold into diverse secondary and tertiary structures and perform multiple functions. Messenger RNA (mRNA) carries genetic information transcribed from DNA to ribosomes, where it is translated into proteins. Transfer RNA (tRNA) acts as an adaptor, pairing specific amino acids with codons on the mRNA during translation. Ribosomal RNA (rRNA) forms the core of ribosomes and catalyses peptide bond formation. Beyond the classical roles, many small and long noncoding RNAs regulate gene expression; microRNAs and small interfering RNAs modulate mRNA stability and translation, while long noncoding RNAs can influence chromatin structure. Some RNA molecules act as enzymes, such as self‑splicing introns, RNase P and the peptidyl transferase activity of the ribosome, demonstrating that RNA can store information and catalyse reactions. RNA genomes are found in many viruses, including influenza, rabies and SARS‑CoV‑2, where viral RNA serves both as genetic material and template for replication.
Types and Functions
mRNA conveys coding sequences from genes to ribosomes; eukaryotic mRNAs are capped and polyadenylated for stability and nuclear export. tRNA molecules have characteristic cloverleaf structures and carry anticodons complementary to mRNA codons. rRNA combines with proteins to form the small and large ribosomal subunits, orchestrating translation. Small nuclear RNAs (snRNAs) participate in splicing, while small nucleolar RNAs (snoRNAs) guide chemical modifications of rRNA. Regulatory RNAs, including microRNAs and siRNAs, fine‑tune gene expression, and long noncoding RNAs influence chromatin and transcription. Viral RNAs can be positive‑sense or negative‑sense strands, requiring specific replication strategies. These diverse roles underscore the versatility of RNA in cellular and viral biology.
RNA is a fundamental molecule bridging genetic information and cellular function. Its structural diversity and catalytic potential underpin processes ranging from protein synthesis to gene regulation and viral replication.
Related Terms: DNA, mRNA, tRNA, Transcription, Ribosome