Genetic effects of oxidative damage from ionizing radiation

    Radiation-induced oxidation of guanine bases produces 8-oxo-7-hydro-guanine (GO). The undamaged strand (left, top) replicates normally and reproduces the standard allele (bottom). The GO base in the damaged strand (middle) pairs with an A during replication of the new strand (grey). Note that this pairs two double-ring purines. Replication of the A strand in the next round of replication results in a C  A transversion mutation with respect to the original DNA (bottom).

    Damaged GO bases may also be repaired by excision repair (right) that removes the GO base and restores the standard G (bottom).