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#translation initiation

13 public questions tagged with this topic.

BOTANY

Which of the following correctly describes the Shine-Dalgarno sequence?

The **Shine-Dalgarno sequence helps in prokaryotic translation initiation** by aligning the ribosome with the start codon. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Botany section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Botany portion (Latest NCERT Textbooks for Academic Session 2026-27 -

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Translation in Prokaryotes and Eukaryotes

Primary role of Kozak sequence is

Surrounding the initiator AUG in vertebrate mRNAs, the consensus GCCRCCAUGG described by Marilyn Kozak provides sequence context that modulates initiation efficiency beyond start codon alone. Positions -3 purine and +4 guanine contact 18S rRNA nucleotides and eIF2alpha subunit, stabilizing codon-anticodon pairing in the P-site and slowing scanning to favor GTP hydrolysis by eIF5 and commitment to 48S complex. Strong Kozak context improves accurate start recognition and reduces leaky scanning to downstream AUGs. Elements governing termination, elongation continuation, and ribosome recycling are

Ref: Alberts Molecular Biology of the Cell 6th Ed Kozak rules; NCBI - Kozak sequence promotes start codon recognition AUG context

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Translation in Prokaryotes and Eukaryotes

Which initiation factor blocks A-site in eukaryotes?

During eukaryotic initiation, preventing premature tRNA entry into the A-site is essential for fidelity and maintaining P-site initiation accuracy. eIF1A, the conserved ortholog of bacterial IF1 sharing OB-fold domain and binding site, binds near the ribosomal A-site on the small 40S subunit, stabilizing an open, scanning-competent conformation and physically blocking the A-site pocket from non-initiator tRNAs. This obstruction ensures only initiator Met-tRNAi occupies the P-site during scanning phases. Upon AUG recognition, eIF1 and eIF1A rearrange and dissociate, vacating A-site for elongati

Ref: NCBI Structure 1HR0 IF1 blocks A-site; Alberts Fig 6-72 - eIF1A occupies A-site to prevent premature tRNA binding

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Translation in Prokaryotes and Eukaryotes

48S complex is formed after

48S pre-initiation complex forms after cap recognition by eIF4F and recruitment of 43S pre-initiation complex to mRNA 5' end. eIF4E binds m7G cap, eIF4G bridges to polyA binding protein circularizing mRNA, then 43S joins near cap and scans 5' to 3' direction inspecting codons in P site. Upon locating AUG in favorable Kozak context, perfect codon-anticodon pairing triggers eIF1 release, GTP hydrolysis by eIF2, Pi release, locking stable 48S complex containing mRNA, 40S and initiator tRNA. Subsequent eIF5B mediated 60S joining yields elongation-competent 80S ribosome.

Ref: Watson Molecular Biology of the Gene, 7th ed., Chapter 15, 48S complex formation after cap recognition and scanning

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Translation in Prokaryotes and Eukaryotes

Eukaryotic equivalent of IF2 is

Bacterial translation initiation factor IF2 is GTPase that delivers initiator fMet-tRNAfMet to 30S P site and promotes joining of 50S subunit. Functional analog in eukaryotes is eIF2, heterotrimeric complex of alpha, beta, gamma subunits where gamma subunit shares sequence homology and G-domain architecture with IF2. eIF2 GTP binds Met-tRNAi forming ternary complex that attaches to 40S subunit with other eIFs. Like IF2, eIF2 hydrolyzes GTP during start codon recognition, and its recycling by eIF2B guanine exchange factor is central regulatory node for stress responses.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 7, eIF2 as eukaryotic functional equivalent of bacterial IF2

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Acid, Base, pH

Consensus Kozak sequence is

G/ANNAUGG is the scientifically accurate answer to this question. Within the study of Acid, Base, pH, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of G/ANNAUGG directly address what is being asked. Among the other options, AGGAGG, TATAAT, and AAUAAA do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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Acid, Base, pH

Kozak sequence is found in

eukaryotic mRNA is the correct answer as it accurately identifies the biological location, composition, or distribution described in this question. In Acid, Base, pH, the spatial organization and localization of molecules are critical to their function. eukaryotic mRNA is specifically associated with the structure or compartment mentioned because of its unique biochemical properties and physiological role. The other options (prokaryotic mRNA, mitochondrial mRNA, and viral DNA) are primarily associated with different cellular compartments, tissues, or structural contexts.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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