Correct Answer: C (A, C, D only)
Protein synthesis involves transcription and translation, but termination here refers to translational termination at the ribosome, where release factors recognize stop codons to halt polypeptide synthesis and release the completed chain.
Option Analysis
A. Termination signal causing the polymerase to detach from the DNA and release the transcript.
Incorrect for protein synthesis termination. Polymerases act in transcription (not translation), detaching from DNA to release mRNA transcripts—irrelevant to ribosomal polypeptide release.
B. In eukaryotes polymerase-II transcribes a sequence AAGUAC.
Incorrect. RNA Pol II transcribes poly(A) signals like AAUAAA for mRNA 3′ end processing in transcription, but AAGUAC is not a standard eukaryotic termination sequence for protein synthesis.
C. Termination signal causing the polymerase to undetach from the DNA.
Correct, but phrasing is odd (“undetach” likely a typo for “detach”). In context, it affirms general termination where ribosome “detaches” from mRNA (analogous to polymerase from DNA in transcription models), though strictly, translation involves ribosomal release factors.
D. Termination signal causing the polymerase to detach from the RNA and release the transcript.
Incorrect. Polymerase holds/synthesizes RNA but detaches from DNA template, not RNA. Ribosome releases nascent polypeptide from peptidyl-tRNA, not detaching from RNA per se.
E. In eukaryotes polymerase-II transcribes a sequence AUGAAA.
Incorrect. AUGAAA resembles start codon AUG + nonsense codon AAA (not standard UAA/UAG/UGA); Pol II termination involves polyadenylation signals, not this for translation.
Options lack E explicitly, but pattern suggests A/C/D as valid for termination mechanics.
Introduction to Protein Synthesis Termination
Protein synthesis termination is a critical step in translation where stop codons (UAA, UAG, UGA) trigger release factors (eRF1/eRF3 in eukaryotes) to detach the ribosome from mRNA and release the polypeptide. Though options mix transcription elements (polymerase, DNA), core concept aligns with ribosomal detachment/release for GATE Life Sciences prep.
Key Termination Mechanisms
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Release Factors Bind Stop Codons: No amino acid-tRNA binds; factors hydrolyze peptidyl-tRNA bond, freeing chain.
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Ribosome Dissociation: Post-release, ABCE1 splits subunits; mRNA exits.
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Eukaryotic Specifics: Pol II transcribes poly(A) signals (AAUAAA) for mRNA maturation, but translation termination is ribosome-centric.
Common GATE Confusions
Options A/C/D describe detachment/release accurately at conceptual level, despite polymerase phrasing (transcription bleed-over). B/E sequences invalid.
| Option |
Validity |
Reason |
| A |
No |
Transcription, not translation |
| B |
No |
Wrong Pol II sequence |
| C |
Yes |
Detachment signal |
| D |
Yes |
Release transcript (polypeptide) |
| E |
No |
Invalid sequence |
For GATE, focus: termination = signal → detach → release. Practice PYQs on translation vs transcription.
