What is Translation (Protein Synthesis)?
Translation is the process by which ribosomes read mRNA codons and link amino acids together to build a polypeptide chain. It is the final step of protein synthesis, turning genetic information carried by mRNA into a functional protein.
Translation is the process where ribosomes decode mRNA codons and use tRNA to bring matching amino acids, linking them into a protein in three stages: initiation, elongation, and termination.
- 1↓InitiationThe small ribosomal subunit binds mRNA; the initiator tRNA (Met) recognizes the start codon AUG.
- 2↓ElongationtRNAs deliver amino acids matching each codon; the ribosome forms peptide bonds and moves along the mRNA.
- 3↓TerminationThe ribosome reaches a stop codon (UAA, UAG, UGA); release factors free the finished protein.
- 4Folding & ProcessingThe new protein folds into its 3D shape and may be chemically modified before becoming functional.
Try it: interactive calculator
Step-by-step worked examples
An mRNA's coding sequence (including the stop codon) is 150 nucleotides long. How many amino acids are in the protein?
L = 150 nt Codons = 150/3 = 50 Remove 1 stop codon → 50 − 1 = 49 amino acids
A gene's mRNA has an open reading frame (ORF) of 300 nt. Find the protein's length in amino acids.
L = 300 nt 300/3 = 100 codons 100 − 1 = 99 amino acids (excludes the stop codon)
A tRNA has the anticodon 3'-UAC-5'. Which mRNA codon does it pair with, and which amino acid does it carry?
Anticodon 3'-UAC-5' pairs antiparallel with mRNA codon 5'-AUG-3' AUG codes for Methionine (the start amino acid) So this tRNA carries Met
Flashcards
Quick quiz
Q1.Which molecule directly carries amino acids to the ribosome during translation?
Q2.How many nucleotides make up one codon?
Q3.Which of these is a stop codon?
Q4.An mRNA ORF is 90 nucleotides long. How many amino acids are in the protein?
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Common mistakes
Thinking translation happens in the nucleus. — Correct: Translation occurs in the cytoplasm/on ribosomes; transcription happens in the nucleus (in eukaryotes).
Believing the stop codon codes for an amino acid. — Correct: Stop codons (UAA, UAG, UGA) have no matching tRNA — they signal the ribosome to release the protein.
Confusing codon and anticodon direction. — Correct: The tRNA anticodon pairs antiparallel to the mRNA codon (3'-5' with 5'-3').
Assuming one ribosome makes many different proteins from one mRNA. — Correct: One mRNA is translated into copies of the same protein; different proteins need different mRNAs.
FAQ
What is translation in protein synthesis?
Translation is the process by which ribosomes decode mRNA codons and link amino acids together to build a protein.
What is the formula to calculate the number of amino acids from mRNA length?
Amino acids ≈ (mRNA coding length ÷ 3) − 1, since one codon is a non-coding stop signal.
What are examples of translation steps?
Initiation (the ribosome assembles at AUG), elongation (tRNAs add amino acids), and termination (a stop codon releases the chain).
How do you calculate protein length from mRNA?
Divide the coding sequence length by 3 to get the codon count, then subtract 1 for the stop codon.