Figure 1.

Effects of DNA damaging agents and DNA repair defects on mitotic crossover rate in Blm mutants. (A) Schematic of method to measure mitotic crossovers. Single males heteroallelic for amorphic Blm mutations and heterozygous for st and e are crossed to tester females. Progeny are scored as being parental (left) or recombinant (right) for st and e. The two recombinant classes are drawn with a crossover in the same position, because we can sometimes recover the two reciprocal products of a single crossover. (B) Frequency of crossovers between st and e in wild-type (pink) and Blm (blue) male germlines after treatment of larvae with the indicated DNA damaging agents. See Materials and Methods for doses. (C) Frequency of male germline crossovers between st and e in various single mutants (pink) and in double mutants with Blm (blue). nd, not done. Error bars are standard error of the mean (n = 16, 35, 9, 14, 25, and 9 males for treatments of Blm in B, left to right; n = 16, 22, 41, 33, 21, 22, 20, and 17 males for Blm mutant genotypes in C). One-way ANOVA test were done to compare each treatment to untreated Blm (B, P < 0.0001) and each double mutant to the Blm single mutant (C, P < 0.0001), with Bonferroni correction for multiple comparisons. Dotted white lines on HN2 and CPT bars indicate values of matched controls. In these cases, unpaired t-tests were done to compare to the matched control (see Materials and Methods). NS, P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001.