How does the concentration of RNA change during the time spent as a pupa?

• A. Fall, rise and fall; rise after 40% and fall after 80%
• B. Rise steadily
• C. Fall and remain low
• D. Constant

Answer: (A)

RNA concentration during metamorphosis reflects shifts in transcriptional activity as tissues are broken down and rebuilt. In the pupal stage, early on transcription tends to drop as larval tissues are dismantled and resources are redirected, leading to a fall in RNA levels. Mid-pupation, there is a surge of gene expression to synthesize and shape the new adult structures, so RNA levels rise. As development nears completion and the major restructuring finishes, transcription declines again, causing RNA to fall once more. This pattern—fall, then rise, then fall, with the rise occurring around the middle of the pupal period (after about 40%) and the fall coming again toward the end (around 80%)—fits the observed dynamics well. Other options imply a monotonic or constant pattern, which doesn’t align with the coordinated waves of transcription needed for tissue remodeling and adult formation.