Effect of temperature on crossing over in the mus309 mutant, deficient in DNA double-strand break repair, of Drosophila melanogaster suggests a mechanism for crossover interference

Crossing-over frequencies, crossover interference, recombination frequencies and map distances were compared in the cv-v-f region of the X chromosome of Drosophila melanogaster in females bearing either wild type 3 chromosomes (control) or having the DNA double-strand break repair deficient mus309/mus309 mutant constitution in the 3 chromosomes (experiment), and raised in three different temperatures viz. 18 ̊C, 25 ̊C and 29 ̊C. In addition, the fecundity of the females was also measured. In the control crosses none of the mean values of the parameters measured was dependent on the temperature, whereas in the experimental crosses all the parameters, except for the frequency of true single crossovers in the cv-v interval, the recombination frequency of the v and f markers, and the coefficient of coincidence, changed due to the effect of temperature. When comparing the genotypes studied, a significant difference between them was observed in all the parameters measured, apart from the frequency of the true single crossovers in the cv-v interval. These results support the counting number model of the mechanism of interference based on the genetic distance, but are in contradiction with the models based on physical distance.