RNA
RNA, or ribonucleic acid, is a nucleic acid that helps cells copy, use, regulate, and sometimes store genetic information. RNA molecules can carry protein instructions, form part of ribosomes, deliver amino acids, regulate genes, catalyze reactions, and serve as genetic material in some viruses.
What RNA is
RNA is one of the two main kinds of nucleic acid, alongside DNA. It is usually single-stranded, but it can fold back on itself through base pairing. That ability to carry sequence information and form useful shapes is why RNA can act as a message, a scaffold, a regulator, and in some cases a catalyst.
RNA structure
An RNA chain is made from ribonucleotides. Each nucleotide contains ribose sugar, a phosphate group, and one nitrogenous base. RNA's bases are adenine, uracil, guanine, and cytosine. The extra hydroxyl group on ribose helps distinguish RNA from DNA chemically and also affects RNA stability and folding.
How RNA differs from DNA
DNA is usually the long-term genetic archive in cells, while RNA is often a working copy, tool, or regulator. DNA is typically double-stranded and uses deoxyribose and thymine. RNA is often single-stranded, uses ribose and uracil, and can be short-lived or heavily processed depending on its job.
Transcription
Cells make RNA by transcription. An enzyme called RNA polymerase reads a DNA template and builds a complementary RNA strand. In protein-coding genes, that RNA can become messenger RNA. Other genes produce noncoding RNAs that do not become proteins but still perform important cell functions.
mRNA, tRNA, and rRNA
Messenger RNA, or mRNA, carries protein-coding instructions to ribosomes. Transfer RNA, or tRNA, matches mRNA codons to the correct amino acids. Ribosomal RNA, or rRNA, forms key parts of ribosomes and helps catalyze peptide bond formation during protein synthesis.
Translation and the genetic code
During translation, a ribosome reads mRNA three bases at a time. Each three-base codon specifies an amino acid or a stop signal. tRNAs bring amino acids to the ribosome, and the ribosome links them into a growing polypeptide chain. This is one way genetic information becomes a physical protein.
Regulatory and noncoding RNA
Not all RNA is translated. MicroRNAs, small interfering RNAs, small nuclear RNAs, long noncoding RNAs, and other RNA classes help process transcripts, silence genes, shape chromatin, guide molecular machines, or tune how much protein a cell makes. Many noncoding RNA functions are still being mapped.
RNA in viruses and medicine
Some viruses use RNA as their genetic material, and retroviruses copy RNA into DNA after infection. In medicine and biotechnology, RNA is used in vaccines, diagnostics, sequencing, gene-silencing tools, and research methods that reveal which genes are active in a cell.
Why it matters
RNA sits at the busy middle of molecular biology. It connects DNA to proteins, helps ribosomes work, regulates gene expression, and gives scientists tools for studying and changing cells. Understanding RNA makes topics like genetics, enzymes, vaccines, viruses, and biotechnology click into place.