Ribosome's Role in Translation — NEET Biology

Correct answer: B — S1, S2 and S4

The question assesses knowledge about the structural and functional aspects of ribosomes and the process of translation. S1: Correct. The concept of a polyribosome (polysome) involves multiple ribosomes translating the same mRNA molecule concurrently, allowing for the synthesis of many identical polypeptides. This is implicitly supported by the text's description of protein synthesis. S2: Correct. NCERT states, "In bacteria, since the mRNA does not require any processing to become active, and also since transcription and translation take place in the same compartment (there is no separation of cytosol and nucleus in bacteria), many times the translation can begin much before the mRNA is fully transcribed. Consequently, the transcription and translation can be coupled in bacteria" (Page 94, Para 3). S3: Incorrect. NCERT states, "There are two sites in the large subunit, for subsequent amino acids to bind to and thus, be close enough to each other for the formation of a peptide bond" (Page 99, Para 2). These are the A (aminoacyl) and P (peptidyl) sites, located on the large ribosomal subunit, not the small one. S4: Correct. "The ribosome also acts as a catalyst (23S rRNA in bacteria is the enzyme- ribozyme) for the formation of peptide bond" (Page 99, Para 2). S5: Incorrect. NCERT clarifies that "The UTRs are present at both 5'-end (before start codon) and at 3'-end (after stop codon)" (Page 99, Para 3). They are not present only at the 5'-end. Therefore, statements S1, S2, and S4 are correct. Option B is the correct answer.