[Tyrosine hydroxylase activity in Drosophila virilis lines with contrasting stress response and in their F1 hybrids].

Activity of tyrosine hydroxylase (TH) was examined in adult flies from stress lines of Drosophila virilis resistant and nonresistant to heat and from their hybrids under heat stress and normal conditions. The resistant line was shown to have higher enzyme activity and dominate for this character. Gene(s) controlling the level of TH activity under normal conditions were not sex-linked. It was shown than 30-min heat stress caused a decrease in TH activity; with 120-min stress, the activity increased. A possible mechanism of these changes is discussed. In the nonresistant line, the TH activity does not change under heat stress; the line dominates at this trait. Gene(s) controlling the level of the enzyme activity under stress are not sex-linked.