Translation (genetics): ribosomes synthesise proteins from mRNA
Translation is the cellular process that decodes messenger RNA to build polypeptides. This article explains its mechanism, components, cellular contexts, and biological significance.
Translation in genetics is the step of gene expression in which the linear code carried by messenger RNA (mRNA) is decoded to assemble a polypeptide chain. It is the central operation of protein biosynthesis and follows upstream events that prepare the mRNA template, including transcription, removal of introns by RNA splicing and the action of spliceosomes.
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Core components and basic mechanism
The machinery that carries out translation is the ribosome, a ribonucleoprotein complex made of small and large subunits that clamp around mRNA. Transfer RNAs (tRNAs) bring specific amino acids to the ribosome; each tRNA presents an anticodon that base-pairs with a complementary mRNA codon. Translation progresses in three broad stages: initiation, elongation and termination.
- Initiation: a ribosomal subunit binds the mRNA at a start codon and recruits the initiator tRNA.
- Elongation: successive tRNAs decode codons; peptide bonds form between adjacent amino acids, extending the growing polypeptide.
- Termination: a stop codon triggers release factors that free the completed chain for folding or further processing.
Cellular context and variations
In eukaryotes translation occurs in the cytoplasm and on ribosomes attached to the rough endoplasmic reticulum, enabling co-translational insertion or import into the secretory pathway. In bacteria, which lack a nucleus, transcription and translation can be coupled: ribosomes begin translating an mRNA while it is still being synthesized. Multiple ribosomes frequently engage a single mRNA to form a polysome, increasing output from one transcript.
Folding, targeting and post-translational events
The linear polypeptide produced by translation must adopt a functional three-dimensional structure to become an active protein. Some proteins fold spontaneously, while others require chaperones. Proteins destined for secretion or for particular compartments are directed into the lumen of the endoplasmic reticulum and packaged into vesicles, which shuttle them between organelles or to the cell surface. Ribosomes on the ER are often associated with the organelle's outer membrane when synthesising membrane or secreted proteins.
Biological importance and applications
Translation implements genetic information encoded in DNA and is essential for virtually all cellular functions. Its accuracy is critical: misreading codons or errors in folding can produce nonfunctional or harmful proteins. The universality and predictability of the genetic code enable biotechnology and medicine to manipulate translation for recombinant protein production, vaccine development and some antibiotics, which target bacterial ribosomes selectively.
Notable distinctions and facts
Although the genetic code is nearly universal, a few organisms and organelles use variant codons. Translation is distinct from, but coordinated with, upstream gene-expression steps such as transcription and splicing. Researchers study ribosome structure and dynamics to understand translation fidelity, regulation and its evolution. For accessible overviews of related topics, see entries on gene expression, transcription and the roles of spliceosomes.
Summary: translation is the decoding of mRNA by ribosomes and tRNAs to synthesise polypeptides, after which folding and cellular trafficking turn polypeptides into functional proteins.
Questions and answers
Q: What is translation?
A: Translation is the second part of protein biosynthesis, which is the process of making proteins. It is part of gene expression and involves the formation of messenger RNA from exons and introns.
Q: Where does translation take place in eukaryotes?
A: In eukaryotes, translation happens on ribosomes in the cytoplasm and endoplasmic reticulum.
Q: How do tRNAs work during translation?
A: During translation, tRNAs with anticodons connect to mRNA's matching codons and carry amino acids. When a tRNA matches with an mRNA, the amino acid that was connected to it gets unconnected from the tRNA and gets connected to the amino acid brought by the previous tRNA.
Q: How does a ribosome work during translation?
A: A ribosome works like a stock ticker and ticker tape during translation. Many ribosomes attach themselves to an outer membrane of rough endoplasmic reticulum along with mRNA, where they make proteins that go into vesicles which then bring them to other organelles or outside of the cell.
Q: What comes before transcription?
A: Before transcription comes gene expression which produces a chain of introns and exons through RNA splicing by spliceosomes which remove introns.
Q: What happens after polypeptides are made during translation?
A: After polypeptides are made during translation, they may need to be combined with other polypeptides so they can form whole proteins or folded before they can function as proteins.
Q: Where does translation take place in bacteria?
A:In bacteria,translation takes place in their cell cytoplasm since they have no nucleus.
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AlegsaOnline.com Translation (genetics): ribosomes synthesise proteins from mRNA Leandro Alegsa
URL: https://en.alegsaonline.com/art/101171