Variation in Dry Mass Concentrations and Protein Contents in DNA Puffs

Abstract

SUMMARYVariations on total dry mass concentrations and relative amounts of histones and non-histone proteins were estimated in the chromosome C of Bradysia hygida salivary glands by means of interferometric, cytophotometric and cytofluorometric procedures.Unpuffed region, C3, used as a control, showed a dry mass value equal to 29.3 × 10−12 g in the various larval phases studied. The regions C4, C5, and C7 displayed dry mass values increased during formation of the DNA puffs and subsequently decreased during puff regression. The region C4 exhibited the largest dry mass values, namely 41.73 times; 10−12 g (m5 phase), 184,50 × 10−12 g (m7+ phase), and 86,53 × 10−12 g (m7+ phase). In this case there was a 53.1% dry mass loss during puff regression, but proteins are not involved in such phenomenon. The data are discussed in terms of the function ascribed for the non-histone proteins concerned with gene activity and chromosome structure.