mu2¹ and mu2¹/Df(3L)Aprt-1 mutants have a similar frequency of single-strand annealing repair (SSA) compared to controls in a P{wIw.FRT} hemizygous assay to study DNA double-stranded break repair when assayed at 38^oC, but show an increased SSA frequency compared to controls when assayed at 32^oC.

Homozygous larvae do not show higher sensitivity to killing by methyl methanesulfonate or radiation than wild type. mu2¹ shows a 6-fold increase in the frequency of total y^- and f^36a spots and a 17-fold increase in the frequency of twin spots in the abdomen of unirradiated y^- + / + f^36a females compared to controls. γ irradiation has no discernible effect on the frequency of spots in mu2¹ females in contrast to wild type.

Lesions induced by γ rays in sperm chromosomes are repaired after fertilisation, while lesions induced in oocyte chromosomes are shunted instead to a mechanism that stabilises broken chromosome ends.

Irradiation of females homozygous for mu2¹ with low doses of X rays produces substantial numbers of terminal deficiencies for all chromosome arms <up>see for example Df(1)yT</up>; irradiation of heterozygous females produces frequencies of deficiencies intermediate between those obtained from homozygous mu2¹ and wild-type females. Extents of deficiencies limited only by the ability to recover them in viable offspring. Incidence of terminal losses linear with dose; such deficiencies visible cytologically and can be shown by in situ hybridization to lack sequences characteristically present at the termini of chromosome arms. Irradiation of mu2¹ females does not increase the incidence of either interstitial deficiencies or sex-linked lethal mutations. Irradiation of mu2¹ males does not increase the frequency of deficiencies.