messenger RNA
Meaning of messenger RNA: One copy can be read many times over before it is destroyed, which is how a single gene yields thousands of protein molecules.
Definition of messenger RNA
Messenger RNA is the working copy of a gene: a single strand of RNA carrying the coded instructions for one protein from the DNA where they are stored to the ribosomes where proteins are assembled. It is produced by transcription, then trimmed and capped before use. The code is read three bases at a time, each triplet naming one amino acid.
What happens between the gene and the protein?
| Step | What happens |
|---|---|
| Transcription | An enzyme copies the gene sequence from DNA into a matching strand of RNA |
| Capping and tailing | A protective cap is added at one end and a long run of adenine bases at the other |
| Splicing | Internal stretches carrying no protein code are cut out and the coding pieces joined |
| Export | The finished molecule leaves the nucleus for the surrounding cytoplasm |
| Translation | Ribosomes travel along the code and assemble the protein it specifies |
Splicing is more than tidying. Coding pieces can be joined in different combinations, so a single gene produces several related proteins depending on which arrangement the cell selects. Bacteria skip most of this: with no nucleus to leave, their ribosomes start reading a transcript while it is still being made.
How long does a molecule last?
Not long, but long enough to be used repeatedly. A single molecule is read by one ribosome after another, often several at once along the same strand, before enzymes dismantle it. Lifespans differ enormously between transcripts, from minutes for those carrying urgent signals to days for the ones a cell needs steadily, and that difference is itself regulated. Controlled breakdown is a way of switching a protein off quickly, which matters because the alternative is waiting for the existing supply to wear out.
How do messenger RNA vaccines use it?
A manufactured strand coding for one protein from a virus is wrapped in a fatty droplet that carries it into cells. The cell's own ribosomes read it and build that protein, the immune system recognizes the protein as foreign and prepares a response against it, and the strand is broken down within days like any other. It never enters the nucleus, and the machinery required to write RNA back into DNA is not present, so the cell's genetic material is untouched.
Also known as
Used in a sentence
Researchers measured messenger RNA levels to determine how strongly the gene was being expressed in the tissue sample.
Good to know
Messenger RNA carries instructions for building a protein but is not incorporated into a cell's permanent genetic material, a distinction central to how messenger RNA based technologies work.