Messenger RNA | Description & Function - Britannica

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Protein synthesis
Protein synthesis Ribosomes are key components of protein synthesis in cells. (more)
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External Websites
  • Institut Pasteur - Discovery of messenger RNA in 1961
  • National Center for Biotechnology Information - Translation of mRNA
Ask the Chatbot a Question Also known as: mRNA, messenger ribonucleic acid Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Dec. 21, 2025 •History Table of Contents Table of Contents Ask the Chatbot

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messenger RNA (mRNA), molecule in cells that carries codes from the DNA in the nucleus to the sites of protein synthesis in the cytoplasm (the ribosomes). The molecule that would eventually become known as mRNA was first described in 1956 by scientists Elliot Volkin and Lazarus Astrachan. In addition to mRNA, there are two other major types of RNA: ribosomal RNA (rRNA) and transfer RNA (tRNA).

protein synthesis1 of 2
protein synthesisDNA in the cell nucleus carries a genetic code, which consists of sequences of adenine (A), thymine (T), guanine (G), and cytosine (C) (Figure 1). RNA, which contains uracil (U) instead of thymine, carries the code to protein-making sites in the cell. To make RNA, DNA pairs its bases with those of the "free" nucleotides (Figure 2). Messenger RNA (mRNA) then travels to the ribosomes in the cell cytoplasm, where protein synthesis occurs (Figure 3). The base triplets of transfer RNA (tRNA) pair with those of mRNA and at the same time deposit their amino acids on the growing protein chain. Finally, the synthesized protein is released to perform its task in the cell or elsewhere in the body. (more)
Messenger RNA2 of 2
Messenger RNAA concept illustration showing two strands of mRNA.(more)

Because information in DNA cannot be decoded directly into proteins, it is first transcribed, or copied, into mRNA (see transcription). Each molecule of mRNA encodes the information for one protein (or more than one protein in bacteria), with each sequence of three nitrogen-containing bases in the mRNA specifying the incorporation of a particular amino acid within the protein. The mRNA molecules are transported through the nuclear envelope into the cytoplasm, where they are translated by the rRNA of ribosomes (see translation).

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RNA polymerase II; messenger RNA
RNA polymerase II; messenger RNAIllustration of an RNA polymerase II molecule, an enzyme in mammalian cells that catalyzes the transcription of DNA into messenger RNA.(more)

In prokaryotes (organisms that lack a distinct nucleus), mRNAs contain an exact transcribed copy of the original DNA sequence with a terminal 5′-triphosphate group and a 3′-hydroxyl residue. In eukaryotes (organisms that possess a clearly defined nucleus) the mRNA molecules are more elaborate. The 5′-triphosphate residue is further esterified, forming a structure called a cap. At the 3′ ends, eukaryotic mRNAs typically contain long runs of adenosine residues (polyA) that are not encoded in the DNA but are added enzymatically after transcription. Eukaryotic mRNA molecules are usually composed of small segments of the original gene and are generated by a process of cleavage and rejoining from an original precursor RNA (pre-mRNA) molecule, which is an exact copy of the gene. In general, prokaryotic mRNAs are degraded very rapidly, whereas the cap structure and the polyA tail of eukaryotic mRNAs greatly enhance their stability.

polynucleotide chain of deoxyribonucleic acid (DNA) More From Britannica nucleic acid: Messenger RNA (mRNA) The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Kara Rogers.

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