[A change in the puff spectrum during development of Drosophila virilis].

The puff spectrum has been studied in the salivary gland chromosomes of D. virilis from 48 hrs of the 3rd larval until the gland lysis. 142 puffs were observed in the D. virilis genome. Among them, 43% were observed at all developmental stages and other puffs were unstable: 47.1% appear at a certain stage and degrade or remain until the gland lysis; 9.9% are characterized by the "pulse" activity, i.e. they appear at a certain stage, degrade and reappear. The number of newly appeared puffs exceeds that of fully degraded ones, i.e. the number of puffs during the gland development until its lysis increases constantly. At the stage of puparium formation, sexual differences in the puff length were found: puffs were longer in males than in females.