Effects of ecdysterone in polytene chromosomes of Trichosia pubescens.

Injection of ecdysterone into mid-fourth instar larvae of Trichosia pubescens brought about drastic changes in the puffing pattern of the chromosomes of the salivary gland. The puff sequence induced by the hormone is quite similar to that which normally occurs at the end of larval life. Three classes of puffs were observed: the early induced, the late induced, and those repressed by the hormone. Among the late-induced puffs, several were DNA puffs. The protein synthesis inhibition prevents the induction of all late puffs and the process of gene amplification but does not affect the induction of the early puffs.