The researchers’ conclusions about flagella regrowth include actinomycin and puromycin experiments. Which statement best matches the evidence?

• A. Actinomycin has no effect on flagella regrowth even when transcription is prevented; puromycin shows little initial effect.
• B. Actinomycin stops regrowth immediately.
• C. Puromycin prevents regrowth at all times.
• D. Transcription continues unaffected during regrowth.

Answer: (A)

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.