Which of the following occurs minutes to hours after exposure to ionizing radiation?

The appearance of atypical cells is indeed a process that can occur within minutes to hours following exposure to ionizing radiation. When cells are exposed to such radiation, their DNA can become damaged, leading to the disruption of normal cellular processes. This damage can manifest morphologically as atypical cells, which are characterized by abnormal shapes, sizes, or structures when viewed under a microscope.

In contrast, functional damage and morphological changes typically require a longer duration to manifest because the effects of radiation on cell function and structure may take more time to develop. Similarly, cataract formation is a delayed effect that often occurs years after exposure, as it takes a significant period for the cumulative damage to affect the lens of the eye.

Therefore, while all the options relate to consequences of radiation exposure, the appearance of atypical cells is unique in its relatively quick onset compared to the other effects listed.