Control of transcription by attenuation occurs in prokaryotes but not in eukaryotes.

Why Attenuation Is Unique to Prokaryotes

Control of transcription by attenuation is the correct answer because it relies on coupled transcription-translation, which only prokaryotes enable due to lacking a nucleus. In prokaryotes like E. coli, a ribosome’s speed on nascent mRNA dictates RNA polymerase pausing at hairpin structures in the leader sequence, often terminating transcription prematurely for genes like the trp operon when tryptophan is abundant. Eukaryotes separate these processes across nuclear and cytoplasmic compartments, preventing such attenuation mechanisms.

Option Breakdown

Protein Phosphorylation

This process modifies proteins by adding phosphate groups and occurs in both cell types for signaling and regulation. Prokaryotes use it in two-component systems (e.g., histidine kinases), while eukaryotes rely on it extensively in kinase cascades like MAPK pathways.

RNA Polymerase and Promoter Interaction

Both prokaryotes and eukaryotes initiate transcription this way, though details differ. Prokaryotic RNA polymerase binds directly to -10 and -35 promoter boxes via sigma factors; eukaryotic RNA polymerase II requires multiple transcription factors (e.g., TBP at TATA box) for pre-initiation complex assembly.

Formation of Okazaki Fragments

DNA replication on the lagging strand produces these short fragments in both domains of life due to antiparallel strand synthesis. Prokaryotes use DNA polymerase III and ligase; eukaryotes use pol δ/ε and equivalent enzymes, with similar 5’→3′ synthesis limits.