A2 Genetic Control and Gene Expression Practice Test 2026 – Complete Exam Prep

Regrowth can begin without turning on new gene expression, which is what these inhibitors test. Actinomycin blocks transcription, so if flagella start regrowing even when transcription is stopped, then making new mRNA isn’t required for the initial regrowth. Puromycin blocks translation, so a little or no immediate effect means that the early steps of regrowth don’t depend on making new proteins from new mRNA right away; the process can use existing proteins and components. Put together, this pattern shows that the initial phase of flagellar regrowth does not require new transcription or new protein synthesis, though later stages might still rely on gene expression and protein production.