Messenger RNA
Say it: MES-in-jur ar-en-AY
Messenger RNA is the RNA copy of a gene that carries protein-building instructions from DNA to the ribosomes, where it is read in three-base codons.
Also: mRNA, messenger ribonucleic acid
Definition
What is Messenger RNA?
Messenger RNA (mRNA) is a single-stranded RNA molecule that carries the coding information of a gene to the ribosomes, the cell's protein-making machines. It is made during transcription, when the enzyme RNA polymerase copies one strand of a gene's DNA. In eukaryotic cells the DNA stays inside the nucleus, so mRNA acts as a portable working copy of the message that can travel out into the cytoplasm.
In eukaryotes the first transcript, called pre-mRNA, is processed before it leaves the nucleus. A modified guanine cap is added to the 5' end, a tail of about 200 adenine bases is added to the 3' end, and introns are cut out by splicing so that the exons join up. The cap and tail protect the molecule and help ribosomes recognize it. During translation, the ribosome reads the mRNA from 5' to 3' in codons, three-base units that each specify an amino acid or a stop signal, starting at an AUG start codon.
mRNA is short-lived, lasting seconds in bacteria and hours in eukaryotic cells, which lets cells adjust protein production quickly. Measuring all the mRNAs in a sample, as RNA sequencing does, shows which genes are active.
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Related
Terms that go with it
- TranscriptionTranscription is the process in which a cell copies the DNA sequence of a gene into a matching strand of RNA.
- TranslationTranslation is the process in which a ribosome reads the codons of a messenger RNA and links amino acids in that order to build a protein.
- CodonA codon is a sequence of three nucleotides in DNA or messenger RNA that stands for one amino acid or tells the ribosome to stop.
- RNA splicingRNA splicing is the step in which introns are cut out of a newly made RNA and its exons are joined, producing a mature RNA ready for use.
- RibosomeA ribosome is a molecular machine of RNA and protein that reads messenger RNA and joins amino acids in the order it specifies to build a protein.
- RNA sequencingRNA sequencing (RNA-seq) is a method that uses high-throughput sequencing to identify and count the RNA molecules in a sample.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- NHGRI Talking Glossary: Messenger RNA (mRNA)
- OpenStax Biology 2e, 15.4 RNA Processing in Eukaryotes
- OpenStax Biology 2e, 15.1 The Genetic Code
- MedlinePlus Genetics: How do genes direct the production of proteins?
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