118 public questions tagged with this topic.
Peptidyl transferase is an enzyme that catalyzes the formation of peptide bonds between amino acids during translation. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
Aminoacyl-tRNA synthetase catalyzes the attachment of an amino acid to its corresponding tRNA. 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 -
Translation does **not** produce **DNA from RNA**; it converts **mRNA into protein**. This follows from NCERT principle where relation explains outcome clearly for students.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Biology - Botany portion covering relevant concept, Topic: Plant structure, physiology and applications.
tRNA is synthesized by RNA polymerase III, not RNA polymerase II. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
AUG is the start codon, coding for methionine, and serves as the initiation signal for translation. 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 -
Messenger RNA (mRNA) carries the genetic code from DNA to ribosomes during protein synthesis.
Ref: NCERT Class 12 Chemistry > Chapter 14: Biomolecules > Topic: Nucleic Acids - Types and Functions - DNA, RNA
Transfer RNA (tRNA) carries specific amino acids to the ribosome for protein synthesis.
Ref: NCERT Class 12 Chemistry > Chapter 14: Biomolecules > Topic: Nucleic Acids - Types and Functions - DNA, RNA
Messenger RNA vaccines represent nucleic acid platform delivering synthetic mRNA encoding pathogen antigen directly to host cytoplasm where host ribosomal machinery translates it transiently. Manufacturing involves in vitro transcription using T7 RNA polymerase from linearized plasmid DNA template encoding spike protein, incorporation of modified nucleoside N1 methylpseudouridine replacing uridine reducing TLR7 mediated inflammation and increasing translation half-life, addition of 5' cap 7-methylguanosine via vaccinia capping enzyme and 2'O-methylation, and 3' polyadenine tail 100 nt for stability. mRNA encapsulated in lipid nanoparticles LNP composed of ionizable lipid ALC-0315 or SM-102 protonated at low pH encapsulating RNA, helper lipid DSPC forming bilayer, cholesterol fluidity, and PEGylated lipid reducing aggregation and prolonging circulation. Upon intramuscular injection LNPs fuse with cell membrane or endocytosed, ionizable lipid becomes cationic at endosomal low pH disrupting endosome releasing mRNA to cytosol. Ribosomes translate antigen protein undergoing post translational modifications, secreted or membrane anchored, processed for MHC I and II presentation inducing neutralizing IgG and CD4 Th1 and CD8 cytotoxic memory. mRNA degraded within days by RNases no integration risk enabling rapid design.
Ref: Pardi et al. Nat Rev Drug Discov 2018 mRNA mechanism; Polack NEJM mRNA; CDC mRNA work.
Prokaryotic translation machinery centers on 70S ribosome sedimenting at 70 Svedberg units, approximately 2.5 MDa particle comprising small 30S subunit containing 16S rRNA about 1542 nucleotides and 21 ribosomal proteins responsible for decoding mRNA via Shine-Dalgarno interaction pairing with anti-Shine-Dalgarno near 3 prime end of 16S, and large 50S subunit containing 23S rRNA 2900 nucleotides, 5S rRNA, and 33 proteins harboring peptidyl transferase center catalyzing peptide bond formation and exit tunnel guiding nascent chain. Initiation uses initiation factors IF1, IF2, IF3 and formyl-methionine tRNAfMet recognizing start codon, elongation factors EF-Tu and EF-G hydrolyze GTP ensuring decoding accuracy. 40S and 60S are eukaryotic cytoplasmic subunits assembling into 80S ribosome, distinct in rRNA expansion segments and protein composition including larger size. Mitochondrial and chloroplast ribosomes are 55-70S retaining bacterial ancestry, explaining antibiotic sensitivity to bacterial-specific drugs. Clinically important, aminoglycosides, tetracyclines, chloramphenicol and macrolides selectively inhibit bacterial 70S initiation and elongation without blocking cytosolic 80S, enabling selective toxicity for antimicrobial therapy.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 6: 70S Bacterial Ribosomes and Antibiotics.
Protein sorting depends on presence of N-terminal signal sequence or internal transmembrane domain. Secretory proteins like insulin, lysosomal cathepsins, plasma membrane receptors and Golgi glycosyltransferases harbor hydrophobic signals recognized by signal recognition particle leading to Sec61 engagement and translocation into ER lumen or membrane, then onward transport, removed from cytosol. Absence of signal leaves nascent chain completing synthesis on free ribosomes in cytoplasm where folding by Hsp70 and TRiC chaperonin occurs. Cytoskeletal proteins actin forty three kDa forming seven nanometer microfilaments and spectrin alpha beta tetramer crosslinking cortical actin belong to this cytosolic class, assembling into meshwork under plasma membrane regulating shape, not entering ER. Experimental fractionation shows actin mRNA enriched in free polysomes versus membrane-bound polysomes, puromycin release independent of microsomes, resistance to protease protection assay. Thus actin and spectrin exemplify ribosome-free cytoplasmic proteins distinct from secretory cohort that require ER entry for modifications. Integration with cell cycle kinases, calcium signaling and mechanical cues ensures coordinated remodeling during growth, migration and differentiation.
Ref: Blobel Nobel Lecture; signal sequence free vs membrane-bound polysomes actin spectrin cytosolic.
Endosymbiosis is supported by mitochondrial translation apparatus resembling bacteria. Mitochondrial ribosomes, mitoribosomes, in mammals sediment as fifty five S composed of twenty eight S small and thirty nine S large subunits, total mass two point seven megadaltons, containing two rRNAs and about eighty two proteins where only thirty percent homologous to bacterial proteins and rest mitochondria-specific adaptations for membrane protein synthesis. They retain bacterial features such as leaderless initiation, formylmethionine start, lack of five prime cap, and sensitivity to tetracycline, chloramphenicol, erythromycin that block bacterial seventy S but leave cytosolic eighty S unaffected, explaining antibiotic side effects like mitochondrial toxicity. They translate thirteen highly hydrophobic subunits of respiratory chain encoded by mtDNA remaining from endosymbiont genome. Evolution retained minimal genome but imported most ribosomal proteins from nuclear genome via TOM/TIM translocases. No similarity to nuclear envelope constituents or cytosolic RNA granules which contain different RNA processing complexes. Structural cryo-EM reveals bacterial core decorated with extra protein shell accommodating insertion into inner membrane via Oxa1 insertase.
Ref: Gray Annu Rev Genet; mitochondria endosymbiont mitoribosome 55S homologous to bacterial 70S.
Eukaryotic ribosome biogenesis is highly compartmentalized energy intensive process. Initiation occurs in nucleolus where RNA polymerase I synthesizes forty seven S precursor containing eighteen S, five point eight S, twenty eight S rRNAs, processed by small nucleolar ribonucleoproteins catalyzing cleavages, methylations and pseudouridylations concurrent with association of imported ribosomal proteins. Resulting pre-forty S and pre-sixty S particles undergo remodeling by assembly factors such as Nob1, Rio2, Rix1 in nucleoplasm ensuring correct folding. These immature subunits are exported through nuclear pores via exportin CRM1 interacting with adapter Nmd3 and Ran-GTP. Cytoplasmic maturation involves final eighteen S cleavage by Nob1, removal of anti-association factors Tif6 and eIF6, binding of functional ligands and quality proofreading. Rough ER hosts translation by mature ribosomes but not biogenesis; lysosomes, peroxisomes, Golgi degradative and modifying roles not synthesis. Disruption at any stage triggers nucleolar stress stabilizing p53 via MDM2 sequestration, linking growth to ribosome production capacity regulated by mTOR signaling.
Ref: Thomson Annu Rev Biochem; ribosome biogenesis nucleolus export pre-subunits CRM1 cytoplasmic maturation.
