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Messenger RNA, or mRNA, is a single-stranded molecule that carries genetic information from DNA to the ribosome, where it serves as a template for protein synthesis. The process of creating mRNA from a DNA template is called transcription, and it occurs in the nucleus of eukaryotic cells. In prokaryotic cells, transcription and translation occur in the cytoplasm.

mRNA molecules are composed of a sequence of nucleotides, each containing a ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and uracil (U). The sequence of these bases determines the order of amino acids in the protein that will be synthesized.

The genetic code is read in triplets of nucleotides called codons. Each codon specifies a particular amino acid, or a start or stop signal for translation. There are 64 possible codons, but only 20 standard amino acids. This means that the genetic code is degenerate, with some amino acids being specified by more than one codon.

Once transcribed, mRNA molecules are transported out of the nucleus (in eukaryotes) to the ribosomes in the cytoplasm. Here, transfer RNA (tRNA) molecules, each carrying a specific amino acid and possessing an anticodon that is complementary to an mRNA codon, bind to the mRNA. The ribosome then catalyzes the formation of peptide bonds between the amino acids, creating a polypeptide chain that folds into a functional protein. mRNA molecules are relatively short-lived and are degraded after they have served their purpose. This allows cells to regulate protein synthesis in response to changing needs.