Visualization of RNA Synthesis on Chromosomes

Abstract

Publisher Summary The numerous electron microscope autoradiographic studies of eukaryotic cells show that RNA synthesis is localized in dispersed chromatin in both nucleolar and non-nucleolar compartments of the nucleus. Alternatively, autoradiography of thin sections of pulse-labeled bacteria shows the localization of RNA synthesis near the interface of the ribosome-containing areas of the cell and the nucleoid regions that contain most of the bacterial DNA. An example of the structural resolution of genetic activity obtainable by thin-sectioning methods is presented in this chapter. In none of the thin-section studies with either eukaryotic or prokaryotic cells, however, could a distinct genetic unit be resolved within the regions active in RNA synthesis. More recently, direct visualization of the fine structure of individual, active genes in both cell types has been accomplished through novel isolation techniques. This chapter discusses the current status of these studies. Structural aspects of the activity of specific genes are demonstrated here using representatives of both eukaryotic and prokaryotic cell types. In both cases, inherent characteristics of the cells permitted the use of relatively simple techniques for isolating portions of active genomes.