Balbiani Ring Activities in Acricotopus lucidus

Abstract

The normal course of somatic cell division is such that all cells of a multicellular organism should possess the same genetic constitution. This fact seems to be in contradiction to the functional diversity among cells of higher organisms. The nowadays generally accepted explanation of this apparent paradox lies in the assumption that cell differentiation arises by differential activation of the genome, i. e. by activation and/or inactivation of different sets of genes. Convincing evidence to support this view comes from the study of the puffing phenomenon in Dipteran giant chromosomes. Puffs have been shown to be specific in relation to both time and developmental stage. Beermann’s (1952) interpretation that puffing in polytene chromosomes is the visible manifestation of local gene activity has become well established in the last 20 years from numerous cytological and biochemical findings in several species of Diptera. Moreover, giant chromosomes provide a suitable model object for studying the regulation of gene activity at the chromosomal level, especially in relation to the topography of the chromosome.KeywordsSalivary GlandSide LobeAnterior LobeMain LobeBalbiani RingThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.