Molecular Inheritance: Transcription & Translation — NEET Biology

Correct answer: B — S3 and S4 are correct

This question examines the reasons and characteristics of transcription-translation coupling, distinguishing between prokaryotic and eukaryotic gene expression. S1: Incorrect. The coupling is facilitated because prokaryotic mRNA *does not* require extensive post-transcriptional modifications, unlike eukaryotes. This statement describes the opposite situation. S2: Incorrect. In prokaryotes, translation can begin *before* the mRNA is fully transcribed, which is a defining feature of coupling. The statement claims it only happens after complete transcription. S3: Correct. NCERT states, '...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.' S4: Correct. NCERT highlights that in eukaryotes, 'It is the fully processed hnRNA, now called mRNA, that is transported out of the nucleus for translation', implying a clear spatial and temporal separation between nuclear transcription/processing and cytoplasmic translation. S5: Incorrect. The *absence* of splicing in prokaryotic mRNA is one factor that *enables* coupling, as it eliminates a processing step. The statement's phrasing, 'which is a prerequisite for coupling', is misleading and implies that splicing itself is needed for coupling, which is contrary to the role of its absence. Therefore, statements S3 and S4 are correct.