A Prodromus to the Genetic Analysis of Puffing in Drosophila
This extract was created in the absence of an abstract.
Excerpt
The topographical analysis of RNA synthesis in the nuclei of eucaryotic cells is rarely possible since the template itself is, at least at the level of the optical microscope, in an apparently disorganized state. Doubtless we shall eventually be able to interpret the organization of interphase chromatin as seen in the majority of cell types; indeed recent progress in preparatory techniques for the electron microscope augers well for such an analysis (see Miller et al., this volume). In a few cell types, for example the oocytes and spermatocytes of animals with lampbrush chromosomes (Callen, 1963; Hess and Meyer, 1968) and in those tissues, especially of the diptera, with polytene chromosomes (Beermann, 1962, for review), experimental analysis of the control of transcription at discrete, recognizable, gene loci is now possible.
Polytene Chromosomes
The characteristic banded appearance of polytene chromosomes reflects their underlying structure. Each polytene chromosome is a composite element which...
