Which category of cells is considered the least sensitive to radiation?

Specialized mature cells are considered the least sensitive to radiation due to their more differentiated and stable nature. Unlike immature or undifferentiated cells, which have high metabolic activity and rapid division, specialized mature cells have typically reached a stage where they are fully developed and have specific functions within tissues. This maturation makes them less likely to be adversely affected by radiation, as they do not actively divide or replicate as frequently as immature cells or active dividing cells. Moreover, specialized cells are generally more resilient to damage because they are better equipped to handle stressors, including radiation exposure, compared to their less differentiated counterparts.

In contrast, immature cells and active dividing cells are highly sensitive to radiation because these cells are in stages of growth and division, where DNA is more vulnerable to damage. Undifferentiated cells, being still in development, also exhibit a high sensitivity due to their active proliferation and metabolic activity. Therefore, the characteristics of specialized mature cells lead to their classification as the least sensitive to radiation.