[Genetic recombination and steroid metabolism in Drosophila].

A double-species ecologo-genetical model, including Drosophila and yeast, has been used as a new methodological instrument for investigation of the physiological mechanism of recombination. Incubation of Drosophila females in the medium containing yeast of the strain mutant for ergosterol synthesis leads to suppression of temperature-induced crossing over. The mass-spectrum analysis of steroid fraction from Drosophila females has shown that incubation of the yeast medium without ergosterol results in arrest of ecdysterone synthesis. These data are explained by the absence of ecdysterone synthesis precursor in the fly organism. The endocrinal control of crossing over is discussed in the light of hormonal regulation of meiosis.