Nuclease Action, Protease Action and Histochemical Tests on Salivary Chromosomes of Drosophila

Abstract

There is considerable evidence for the presence of both nucleic acids and proteins in the salivary gland chromosomes of certain diptera.The so- called "euchromatic" bands stain intensely after application of the Feulgen- Rossenbeck technique, which is a fairly specific test for the pentose of animal nucleic acids.The heterochromatic regions also give a weak re- action, and the boundaries between the bands are not sharp.'Caspersson2 found that the material of the euchromatic bands had a similar ultra-violet absorption spectrum to the nitrogenous bases characteristic of nucleic acids.There is little doubt, therefore, that the euchromatic bands are regions of high nucleic acid concentration.The presence of proteins in the chromosomes has been demonstrated by Caspersson, who found that the heterochromatic bands could be digested by trypsin, the euchromatic bands also being visibly affected.The results of Barigozzi,3 who stained salivary gland chromosomes of Chironomus with Millon's reagent, indicated the presence of protein along the chromosome, but this author found it impossible to observe much detail in his prepara-