Translation
Molecular Biology · Biochemistry · Cell Biology
Say it: tranz-LAY-shun
Translation 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.
Also: protein synthesis
Definition
What is translation?
Translation is the second stage of gene expression, after transcription. A ribosome, a large machine made of RNA and protein, travels along a messenger RNA (mRNA) and reads it one codon, or three bases, at a time. Transfer RNAs (tRNAs) act as adaptors: each carries a particular amino acid and has an anticodon that pairs with a matching codon, so amino acids line up in the order the gene dictates.
It starts when the small ribosomal subunit finds the start codon, AUG, and an initiator tRNA carrying methionine (a formylated form in bacteria) pairs with it; the large subunit then joins. During elongation, each new tRNA enters the A site, the growing chain is held in the P site, and empty tRNAs leave from the E site. Ribosomal RNA itself forms each peptide bond, and GTP powers the movements. When a stop codon arrives, a release factor frees the finished polypeptide.
Translation takes place in the cytoplasm, on free ribosomes or on those bound to the rough endoplasmic reticulum. Several ribosomes can read one mRNA at once, and the new chain is usually folded and modified before it works.
Word parts
Where does the word “translation” come from?
- trans-
- acrossLatin trans
- -lat-
- carriedLatin latus, past participle of ferre, to carry
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- 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.
- Messenger RNAMessenger 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.
- Transfer RNATransfer RNA is a short adaptor RNA that brings a specific amino acid to the ribosome and pairs with the matching mRNA codon through its anticodon.
- 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.
- Peptide bondA peptide bond is the covalent link that joins the carboxyl group of one amino acid to the amino group of the next, releasing a water molecule.
- Post-translational modificationA post-translational modification is a chemical change made to a protein after it is built on the ribosome, often altering its activity or location.
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