[Age specificity of the effect of 5-bromdeoxyuridine on the differentiation and spectra of chromosomal puffs in the salivary glands of Drosophila virilis Sturt. II. Alteration of the puff spectrum in salivary gland chromosomes].

The expressivity and temporal patterns of function of the various puff groups are changed, when larvae of Drosophila virilis are kept on BUdR containing medium during different periods of their larval development, as compared with the control animals kept on BUdR-free media. The magnitude of the effect depends on the stage at which the treatment is conducted; the larvae of the 3rd instar are more sensitive to BUdR. The effect of BUdR becomes considerably lower by the end of the 3rd instar period.