Why do different organs in mammals show different gene activity patterns related to longevity?

Answer: Each organ follows its own maintenance schedule and stress response

Body size sets the pattern of gene activity in every organ — Wrong. Body size influences overall lifespan but does not explain why gene activity patterns differ between organs. A large animal and a small one both show tissue-specific patterns; size alone cannot account for the molecular differences observed in liver, kidney, and brain.

Each organ follows its own maintenance schedule and stress response ✓ — Correct! Different organs have distinct maintenance schedules and stress responses, like clocks ticking at different speeds. For example, the brain relies heavily on protein quality control, while the liver focuses on metabolism. This tissue-specific regulation means longevity-related genes are not uniformly active across the body. It's a coordinated but diverse system.

The same genes are active in the same way in all organs — Wrong. If the same genes were active everywhere, we would see strong overlap in longevity-related gene expression across tissues. However, studies show that each tissue uses a unique set of genes and pathways to manage aging, contradicting the idea of a universal genetic program.