Quantitative effects of P elements on hybrid dysgenesis in Drosophila melanogaster.
Genetic analyses involving chromosomes from seven inbred lines derived from a single M' strain were used to study the quantitative relationships between the incidence and severity of P-M hybrid dysgenesis and the number of genomic P elements. In four separate analyses, the mutability of snw, a P element-insertion mutation of the X-linked singed locus, was found to be inversely related to the number of autosomal P elements. Since snw mutability is caused by the action of the P transposase, this finding supports the hypothesis that genomic P elements titrate the transposase present within a cell. Other analyses demonstrated that autosomal transmission ratios were distorted by P element action. In these analyses, the amount of distortion against an autosome increased more or less linearly with the number of P elements carried by the autosome. Additional analyses showed that the magnitude of this distortion was reduced when a second P element-containing autosome was present in the genome. This reduction could adequately be explained by transposase titration; there was no evidence that it was due to repressor molecules binding to P elements and inhibiting their movement. The influence of genomic P elements on the incidence of gonadal dysgenesis was also investigated. Although no simple relationship between the number of P elements and the incidence of the trait could be discerned, it was clear that even a small number of elements could increase the incidence markedly. The failure to find a quantitative relationship between P element number and the incidence of gonadal dysgenesis probably reflects the complex etiology of this trait.
Rasmusson
K E
KE
Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108-1095.
Simmons
M J
MJ
Raymond
J D
JD
McLarnon
C F
CF
D000818:Animals; D003433:Crosses, Genetic; D004251:DNA Transposable Elements; D004331:Drosophila melanogaster / Q000235:genetics* / Q000502:physiology; D005260:Female; D005298:Fertility; D008297:Male; D009154:Mutation; D009713:Nucleotidyltransferases / Q000378:metabolism; D019895:Transposases
D004251:DNA Transposable Elements; D009713:Nucleotidyltransferases; D019895:Transposases