You accidentally exposed your cell culture dish to radiation, but you are not sure of the precise ...

Any radiation energy in wavelengths shorter than 380 nm is mutagenic. Ultraviolet radiation is a commonly encountered mutagen that creates pyrimidine dimers in DNA, and these can lead to base-pair substitution mutations. If the dimer cannot be removed, it may also lead to replication stalling at the site of the lesion. Replication blockage by pyrimidine dimers may induce reinitiation of DNA synthesis at an adjacent RNA primer site. This reinitiation of replication potentially leaves gaps spanning dozens to hundreds of nucleotides in newly synthesized DNA strands, but the gaps are subsequently filled by translesion DNA synthesis, which is carried out by specialized bypass DNA polymerases that can replicate across the gaps but lack proofreading capabilities.
Higher-energy radiation can induce DNA strand breaks. DNA can be damaged in multiple ways, the most serious being the induction of DNA single-strand or double-strand breaks. These breaks potentially block DNA replication and thus pose a significant threat to the integrity and survival of affected cells. DNA damage of this type is dealt with by specialized strand-break repair mechanisms. Double-strand DNA breaks are often the most difficult to repair and thus are the most lethal to cells.