What characteristic is most significant in determining the impact of radiation on a developing organism?

The rate of cell division is particularly significant in determining the impact of radiation on a developing organism because rapidly dividing cells are more sensitive to radiation. During development, many cells are undergoing rapid mitosis as the organism grows and differentiates, making them more vulnerable to damage caused by radiation exposure. This susceptibility arises because radiation can cause DNA damage, and cells that are actively dividing have less time to repair this damage before they proceed with another division.

Furthermore, during critical periods of development, such as embryogenesis, the effects of radiation can result in severe consequences, including malformations or even cell death, which can affect the overall growth and health of the organism. The timing of exposure relative to the phase of cell division is thus a key factor in evaluating the potential risks associated with radiation, emphasizing the importance of the rate of cell division in the context of radiation biology.