Which of the following phenomena may underlie the genetic changes that have been noted in the patient?

A 45-year-old patient who experienced exposure to radiation during an industrial accident several years prior is being assessed. Which of the following phenomena may underlie the genetic changes that have been noted in the patient?
Base pairs may have been rearranged by the radiation exposure.
Endonucleases may have influenced the DNA structure following exposure.
Two paired bases may have exchanged helical positions after the accident.
The radiation may have produced redundant or degenerate genetic code.