Chromosome organization in meiosis revealed by light microscope analysis of silver-stained cores

Abstract

Three species of grasshoppers have been analyzed by means of a modified silver impregnation technique that reveals the presence of a chromatid core that identifies chiasmata at first meiotic metaphase. In terms of the behaviour of the chromatid core most of the configurations observed at diplotene with orcein are easily recognized in metaphase I silver-stained bivalents. Some "hidden" configurations, as well as simple chromatin associations, that do not appear to represent chiasmata have also been detected. The disposition and behaviour of the chromatid cores in metaphase I and anaphase I provide grounds to support a reorganization of half-bivalents between first and second division. Key words: chromatid core, meiotic chromosome organization, chiasma formation, insect cytogenetics.