Structure, frequency and distribution of P elements in relation to P—M hybrid dysgenic male recombination inDrosophila melanogaster

Abstract

SummaryThe frequency and distribution of P elements were investigated in the third chromosomes of two wild-type strains ofDrosophila melanogasterusingin situhybridization of biotinylated probes to the polytene chromosomes. The relationship between these data and the extent of hybrid dysgenesis was determined through assays of egg production, egg hatchability (F2embryo lethality),snwdestabilization and male recombination along the third chromosome. The results suggest that P-element distribution, frequency and structure are all contributory factors in the regulation of hybrid dysgenesis. Texas 6 was shown consistently to be a stronger P strain than Texas 1, eliciting greater reductions in fertility, more extensivesnwdestabilization and higher frequencies of male recombination. Clustering of male recombination events, arising from pre-meiotic crossing over, was evident among the dysgenic progeny of each strain. Male recombination andsnwdestabilization were independently distributed among the dysgenic males studied, suggesting that these traits represent separate P-mediated functions. The third chromosome male recombination maps produced by the two strains differed significantly from each other and from the published female meiotic and polytene chromosome maps. Male recombination breakpoints were associated with the original distribution of P sequences in the two strains and the results suggest that this relationship may be closer for potentially complete P factors than for P sequences in general. An analysis of sub-lines derived from individual recombinant males revealed that chromosomal breakpoints could also be associated with novel insertions following P-element transposition.