When is a cell most sensitive to radiation?

A cell is most sensitive to radiation during mitosis. This phase of the cell cycle is when the cell is actively dividing and its DNA is being replicated and distributed into two daughter cells. The processes that occur during mitosis, including chromosome alignment and separation, involve significant cellular activity and less opportunity for the cell to repair damage. Consequently, radiation exposure during this period can lead to more severe consequences, such as mutations or cell death, because the cellular mechanisms that typically repair DNA damage are not as efficient when the cell is in the midst of division.

In contrast, during interphase, the cell is primarily engaged in growth and normal metabolic activities, which include phases of DNA repair mechanisms that can address potential damage. Apoptosis is a programmed cell death process and is not a phase of the cell cycle concerning sensitivity to radiation. Cytokinesis, although important in the final stages of cell division, occurs after the critical events of mitosis and does not present the same vulnerability to radiological damage as mitosis itself. Hence, the sensitivity to radiation is notably heightened during the mitotic phase.