DNA
High energy waves like x-rays and gamma rays can actually cut one or both strands of DNA. This type of damage is called a double strand break. One double strand break can cause the cell to die. Two common ways the cell fixes this problem is homologous recombination and non homologous end joining. In homologous recombination, enzymes use a similar part of another gene as a template to fix the break. In non-homologous end joining enzymes trim around the place where the DNA strand broke and put them together. This way is much less accurate but works when there is no similar genes available.