Die experimentelle Beeinflussung des Puffmusters von Riesenchromosomen

By treating larvae and prepupae of Ch. thummi with 2 mg/ml oxytetracycline (OTC) about 30 puffs not present in normal development are induced in the salivary gland chromosomes. Already existing puffs become enlarged (cf. Fig. 4). A considerable number of induced puffs appeared in heterozygous condition (cf. Fig. 1a-c). The species Ch. strenzkei does not react in any way to the same treatment. Other inhibitors of protein synthesis such as cycloheximide and chloramphenicole do not influence the puffing pattern in both species. — Animals which had been treated with OTC for 2 hrs show the first signs of puffing. Fully developed OTC-induced puffs are detectable 20 hrs after treatment. At this time the Balbiani rings and the nucleolus are mostly regressed. — Both the induced puffing pattern and the number of heterozygous puffs depend on the genetic constitution of the animals. Animals derived from different locations can be shown to possess different specific spectra of induced puffs. The induced puffing pattern of animals bred from single egg masses is reduced, and heterozygous puffs are rare or absent. — OTC-induced puffs show a strong uptake of tritiated uridine (cf. Fig. 2). Heterozygous puffs are labelled only in the puffed half of the band (cf. Fig. 3).