Messenger RNA (mRNA)
Messenger RNA (mRNA) is a single-stranded RNA molecule that carries genetic information transcribed from DNA and serves as the template for protein synthesis during translation. In eukaryotes, the primary transcript (pre-mRNA) is processed in the nucleus by addition of a 5' 7-methylguanosine cap, a 3' poly-adenylate tail, and removal of non-coding introns by the spliceosome before being exported to the cytoplasm. The lifespan of an mRNA molecule varies from minutes to hours and is tightly regulated, making mRNA abundance a key determinant of gene expression levels.
Structural Features of Eukaryotic mRNA
| Feature | Location | Function | Approximate Length |
|---|---|---|---|
| 5' 7-methylguanosine cap | 5' end | Protects mRNA; aids ribosome binding | 1 modified nucleotide |
| 5' UTR | 5' of start codon | Ribosome binding; translation regulation | 50–200 nt |
| Coding sequence (CDS) | AUG to stop codon | Encodes the protein | Varies (hundreds to thousands nt) |
| 3' UTR | 3' of stop codon | Stability; localization; regulation | 100–1000+ nt |
| Poly-A tail | 3' end | Protects mRNA; aids export and translation | 150–250 adenine residues |
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Related Terms
Transcription (biology)
Transcription is the first step of gene expression in which a specific segment of DNA is copied into RNA (messenger RNA, mRNA) by the enzyme RNA polymerase. The process occurs in the nucleus of eukaryotes and the cytoplasm of prokaryotes, and involves three stages: initiation at the promoter, elongation of the RNA strand, and termination at a specific sequence. The resulting pre-mRNA in eukaryotes undergoes processing (5' capping, polyadenylation, and splicing) before being exported to the cytoplasm for translation.
Translation (biology)
Translation is the process by which a ribosome decodes the nucleotide sequence of a messenger RNA (mRNA) and synthesizes the corresponding sequence of amino acids to produce a polypeptide chain. It occurs in three phases — initiation, elongation, and termination — and takes place at ribosomes in the cytoplasm of both prokaryotes and eukaryotes. The genetic code, read in triplets called codons, determines which amino acid is incorporated at each step, with transfer RNA (tRNA) molecules acting as adaptors between the mRNA codons and the amino acids.
Gene Expression
Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product — most commonly a protein, but also functional RNA molecules such as tRNA, rRNA, and microRNA. It encompasses two main stages: transcription (DNA to mRNA) and translation (mRNA to protein), along with all associated regulatory and processing steps. Gene expression is tightly regulated at multiple levels — transcriptional, post-transcriptional, translational, and post-translational — allowing cells to respond dynamically to developmental cues, environmental signals, and metabolic needs.
Messenger RNA was named by François Jacob and Jacques Monod in 1961 to describe the unstable RNA intermediate that "carries a message" from DNA (the genetic archive) to the ribosome (the protein factory). The abbreviation mRNA became standard shortly after.