Which of the following cellular effects can result from exposure to ionizing radiation (including chromosome breaks, chromatin clumping, and abnormal mitoses)?

• A. 1 and 2
• B. 1 and 3
• C. 1, 2, and 3
• D. 2 and 3

Answer: (C)

Ionizing radiation disrupts cells by damaging DNA and altering chromatin structure. The primary event is DNA damage, including double-strand breaks that manifest as chromosome breaks. As the cell responds to this damage, chromatin can become abnormally condensed or clump together during repair processes, reflecting changes in chromatin organization. If the damage is extensive or misrepaired, chromosomes can be improperly segregated during mitosis, leading to abnormal mitoses with misaligned or lagging chromosomes. Because radiation can produce all of these effects, each of the listed outcomes is possible, so all three can occur.