Final answer:
The start and stop of transcription and translation in prokaryotes are transcribed and translated almost simultaneously because there is no separate nuclear compartment. This allows coupling of transcription and translation, with mRNA being used for protein synthesis promptly after being transcribed. The best answer choice is Option b, and by extension, Option d.
Step-by-step explanation:
Start and Stop of Transcription and Translation in Prokaryotes
In prokaryotes, because genes involved in the same biological process are often grouped together, the start and stop of transcription and translation are transcribed and translated almost simultaneously. This is possible because, unlike eukaryotes, prokaryotes lack a separate nuclear compartment, allowing the processes of transcription and translation to be coupled. As soon as enough mRNA is exposed, a ribosome can bind to start translation before the transcription process has completely finished. This concurrent activity is facilitated by all processes occurring in the 5' to 3' direction and the overall lack of membranous compartmentalization within the prokaryotic cell.
Additionally, in prokaryotes, gene expression begins with the synthesis of mRNA through transcription. Transcription proceeds through three stages which are initiation, elongation, and termination. Once mRNA is synthesized, it can be immediately translated into a protein because there is no nuclear membrane separating these processes. Hence, gene expression and protein synthesis in prokaryotes are tightly linked events.
The correct answer to the fill-in-the-blank question is: transcribed and translated almost simultaneously (Option b), making Option d 'both b and c are true' the comprehensive answer since they are also controlled concurrently by the transcriptional mechanisms in prokaryotic cells.