ribonucleic acid
Meaning of ribonucleic acid: The full chemical name behind the abbreviation RNA, covering every form the cell builds and not only the messenger kind.
Definition of ribonucleic acid
Ribonucleic acid, abbreviated RNA, is one of the two kinds of nucleic acid that cells build, the other being DNA. It is a chain of units called nucleotides and usually exists as a single strand rather than the paired double strand of DNA. Cells make several forms of it, each handling a different part of turning genetic instructions into working proteins.
What forms does a cell make?
| Form | What it does |
|---|---|
| Messenger RNA | Copies the instructions held in a gene and carries that copy to be read |
| Transfer RNA | Brings the correct building block to the growing protein chain, one at a time |
| Ribosomal RNA | Forms the bulk of the ribosome, the structure that assembles proteins |
| Regulatory RNA | Silences particular messages and turns genes up or down |
The first three are the working parts of protein manufacture, and together they account for almost all the RNA in a cell by weight, with the ribosomal form making up the largest share on its own. The fourth group is a broad collection of small and long molecules that never become protein themselves. It is the part of the picture that has grown most as sequencing methods improved, and much of it was dismissed as noise before its role in control was recognized.
How does it differ from DNA?
Three chemical differences separate the two. The sugar in the backbone is ribose rather than deoxyribose, which carries one fewer oxygen atom. The base uracil takes the place of thymine. And the molecule is normally built as one strand rather than two wound around each other, although that single strand folds back on itself and pairs in places, producing the loops and hairpins that give transfer and ribosomal RNA their working shapes. The consequence is practical: deoxyribonucleic acid is stable enough to serve as a permanent archive, while much RNA is made, used and broken down quickly. That is a feature rather than a flaw, because a working copy that persisted would keep producing protein long after the protein was needed.
Why does the full name still appear?
Laboratory reports, patents and formal writing usually spell the term out on first use before switching to the initials. The full name also makes the chemistry explicit in a way the abbreviation hides, naming both the sugar in the backbone and the acidic character that placed it among the nucleic acids. Reading a stretch of RNA gives the order of its bases, and that order specifies an amino acid sequence once the cell translates it. Some viruses carry their genetic material as RNA in place of DNA, and RNA made in a laboratory is used in research and in vaccines and treatments that supply cells with a chosen sequence to work from.
Also known as
Used in a sentence
The vaccine works by introducing a synthetic ribonucleic acid sequence that directs cells to produce a specific protein.
Good to know
Messenger RNA is broken down quickly by design, but ribosomal and transfer RNA are stable and long lasting, so the description of ribonucleic acid as a disposable working copy fits only the messenger form.
Word origin
Where “ribonucleic acid” comes from
Formed from ribose, the five-carbon sugar in its backbone, combined with nucleic acid, a term originally describing acidic compounds isolated from the cell nucleus.