Final answer:
Ionizing radiation damages DNA by causing single and double-strand breaks and modifying DNA bases, leading to potential cancerous changes and tissue damage.
Step-by-step explanation:
The exposure to ionizing radiation, often employed in therapeutic and palliative cancer treatments, leads to DNA damage primarily through the induction of single- and double-strand breaks in the DNA backbone. This occurs as a result of the formation of hydroxyl radicals upon exposure to radiation, which can then interact with DNA. Additionally, ionizing radiation can alter the chemical structure of DNA bases, such as causing the deamination of cytosine into uracil. These changes can lead to disruptions in DNA replication and cell function. Ionizing radiation can not only generate precancerous and cancerous cells due to altered DNA structures and rapid, uncontrolled cell growth but also cause physical tissue damage, which is typical in cases of severe radiation exposure.