What is Translation?
Translation is the process by which ribosomes read an mRNA sequence and build a chain of amino acids into a protein. It is the second major step of gene expression, following transcription, and it happens on ribosomes in the cytoplasm.
Translation is the process of decoding mRNA codons into a specific sequence of amino acids to build a protein, carried out by ribosomes and tRNA.
- 1↓InitiationThe small ribosomal subunit binds the mRNA at the start codon (AUG); initiator tRNA carrying methionine pairs with it, then the large subunit joins.
- 2↓ElongationThe ribosome moves codon by codon along the mRNA; tRNAs deliver matching amino acids and peptide bonds link them into a growing chain.
- 3TerminationThe ribosome reaches a stop codon (UAA, UAG, or UGA); release factors bind instead of tRNA, freeing the finished polypeptide.
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Step-by-step worked examples
An mRNA coding sequence has 300 nucleotides (excluding the stop codon). How many amino acids does it encode?
Amino acids = nucleotides ÷ 3 Amino acids = 300 ÷ 3 Amino acids = 100 amino acids
A finished protein is 150 amino acids long. How many mRNA nucleotides (excluding the stop codon) encoded it?
Nucleotides = amino acids × 3 Nucleotides = 150 × 3 Nucleotides = 450 nucleotides (plus 3 more for the stop codon = 453 total)
The mRNA codon is 5'-AUG-3'. What is the complementary tRNA anticodon, and which amino acid does it carry?
tRNA anticodon pairs antiparallel and complementary to the codon 5'-AUG-3' pairs with 3'-UAC-5' AUG codes for methionine, so this tRNA carries methionine (the start amino acid)
Flashcards
Quick quiz
Q1.Where does translation take place in a eukaryotic cell?
Q2.What is the start codon in translation?
Q3.Which molecule carries amino acids to the ribosome?
Q4.A 600-nucleotide coding mRNA sequence (excluding the stop codon) encodes how many amino acids?
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Common mistakes
Confusing transcription and translation. — Correct: Transcription copies DNA into mRNA in the nucleus; translation reads that mRNA to build a protein at the ribosome.
Thinking each single nucleotide codes for one amino acid. — Correct: Three nucleotides together (a codon) code for one amino acid.
Believing tRNA carries the mRNA message itself. — Correct: tRNA carries individual amino acids and reads the mRNA codons using its own anticodon.
Forgetting that stop codons don't code for an amino acid. — Correct: Stop codons (UAA, UAG, UGA) have no matching tRNA — release factors bind instead and end translation.
FAQ
What is translation in biology?
Translation is the process where ribosomes read mRNA codons and assemble the corresponding amino acids into a polypeptide chain, producing a protein.
What is the translation formula for the number of amino acids?
Amino acids = coding nucleotides ÷ 3, since each codon (3 nucleotides) specifies one amino acid.
What are examples of translation in the body?
Ribosomes translating insulin mRNA in pancreatic cells, or hemoglobin mRNA in developing red blood cells, are classic examples.
How to calculate translation output from mRNA length?
Divide the number of coding nucleotides (excluding the stop codon) by 3 to get the number of amino acids in the resulting protein.