RNA
Ribonucleic acid — a single-stranded molecule that carries genetic instructions from DNA to the cell's protein-making machinery, and serves many other regulatory roles.
RNA (ribonucleic acid) is a nucleic acid similar to DNA but typically single-stranded and using the base uracil (U) instead of thymine (T). It plays multiple critical roles in cells, most famously as messenger RNA (mRNA), which carries genetic instructions from DNA out of the nucleus to the ribosomes where proteins are built.
Beyond mRNA, cells contain transfer RNA (tRNA) that delivers amino acids during protein synthesis, ribosomal RNA (rRNA) that forms the structural and catalytic core of ribosomes, and many regulatory RNAs that control gene expression.
RNA's flexibility — folding into complex shapes, catalysing reactions, carrying information — has made it central to modern biotechnology. mRNA vaccines (like the COVID-19 vaccines) deliver synthetic mRNA that instructs cells to temporarily produce a single viral protein, training immunity without delivering an actual virus.