Translation is the process where amino acids are joined one by one to form a protein (polypeptide). The order of amino acids is decided by the order of codons (base triplets) on the mRNA, and the ribosome does this reading and joining. Memory hook: "Translation = reading the mRNA language and writing it as protein language."
The ribosome moves along mRNA from the start codon (AUG) to the stop codon. Charged tRNAs bring amino acids that are joined by peptide bonds into a polypeptide. The four stages are charging, initiation, elongation and termination.
Your doubts, answered
What is translation in simple words?
Translation is the making of a protein. Amino acids are joined together in a chain (polypeptide) using a peptide bond. The exact order of amino acids is set by the order of bases (codons) in the mRNA. The ribosome is the machine that reads the mRNA and builds the protein.
What is the FIRST phase of translation? (very common NEET trap)
The first phase is aminoacylation of tRNA (also called charging of tRNA). Here each amino acid is activated using ATP and attached to its correct tRNA. This happens BEFORE the ribosome starts reading mRNA. Students wrongly pick 'binding of mRNA to ribosome' — that comes later, in initiation.
When does translation actually begin?
Translation begins the moment the SMALL subunit of the ribosome encounters (meets) the mRNA. NCERT says: 'When the small subunit encounters an mRNA, the process of translation of the mRNA to protein begins.' It is the small subunit, not the large subunit, and not both joining first.
What are the four steps of translation?
1) Activation/charging (aminoacylation of tRNA). 2) Initiation — ribosome binds mRNA at the start codon AUG, read only by the initiator tRNA. 3) Elongation — charged tRNAs pair their anticodon with each codon, amino acids are added one by one, ribosome moves codon to codon. 4) Termination — a release factor binds the stop codon and the finished polypeptide is released.
How is translation different from transcription?
Transcription copies DNA into mRNA (DNA language to RNA language, both use nucleotides). Translation converts mRNA into protein (RNA language to amino-acid language). Transcription happens first and uses RNA polymerase; translation happens next and uses the ribosome and tRNA.
What is a polysome (polyribosome)?
When many ribosomes attach to a single mRNA at the same time and each makes a copy of the polypeptide, this string of ribosomes is called a polysome or polyribosome. This lets one mRNA make many protein copies quickly. NEET 2018 asked this directly.
⚠️ The NEET trap ✗ The first phase of translation is the binding of mRNA to the ribosome. ✓ The first phase of translation is aminoacylation (charging) of tRNA — amino acids are activated with ATP and attached to their tRNA BEFORE the ribosome reads mRNA. 🧠 'Charge before you read.' tRNA is charged first; mRNA binding (initiation) comes after. NEET 2020 answer = Aminoacylation of tRNA.
Real NEET questions
2020
The first phase of translation is:
A · Aminoacylation of tRNA ✓
B · Recognition of an anti-codon
C · Binding of mRNA to ribosome
D · Recognition of DNA molecules
Solution: In the first phase, amino acids are activated using ATP and attached to their correct tRNA — this is called charging or aminoacylation of tRNA. It happens before the ribosome binds mRNA, so option A is correct. (NCERT Ch 5: 'in the first phase itself amino acids are activated... aminoacylation of tRNA'.)
2022
The process of translation of mRNA to proteins begins as soon as:
A · The small subunit of ribosome encounters mRNA ✓
B · The larger subunit of ribosome encounters mRNA
C · Both the subunits join together to bind with mRNA
D · The tRNA is activated and the larger subunit of ribosome encounters mRNA
Solution: The ribosome stays inactive as two subunits. NCERT states translation begins the moment the SMALL subunit meets the mRNA. So the correct answer is A — not the large subunit, and not both joining first.
2018
Many ribosomes may associate with a single mRNA to form multiple copies of a polypeptide simultaneously. Such strings of ribosomes are termed as:
A · Plastidome
B · Polyhedral bodies
C · Polysome ✓
D · Nucleosome
Solution: A string of several ribosomes translating one mRNA at the same time is called a polysome (polyribosome). Nucleosome is DNA packaging, so it is a distractor. Correct answer is C.
Solved Molecular Basis of Inheritance NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Translation takes place on the ribosome, in the cytoplasm. Ribosomes may be free in the cytoplasm or attached to the rough endoplasmic reticulum.
Which molecule carries amino acids to the ribosome?
tRNA (transfer RNA) carries amino acids. Its anticodon pairs with the mRNA codon so the correct amino acid is placed in the growing chain.
What is the start codon and the initiator tRNA?
The start codon is AUG (codes for methionine). It is recognised only by the special initiator tRNA, which starts the protein chain.
What ends translation?
Termination happens when a release factor binds the stop codon (UAA, UAG or UGA). The finished polypeptide is then released from the ribosome.
Is the ribosome an enzyme?
Yes. The ribosome itself acts as a catalyst for peptide bond formation. In bacteria the 23S rRNA of the large subunit is the enzyme, so it is called a ribozyme.
