Influence of chromosome condensation and preparative chromosome methods on chromatid volume

Human metaphase chromosomes 1 and 2 were examined by electron microscopy. Volumetric determinations were calculated on non-treated isolated chromosomes and spread metaphases treated with ammoniacal silver carbonate (ASC). Chromatid volume increased from early-metaphase to late-metaphase and this increase was statistically significant. A similar relationship was found when chromosomes with differentially condensed sister chromatids were studied. The more condensed chromatid volume was greater than its less condensed sister chromatid. ASC treatment produced structural changes in chromosomes which caused an increase of volume in relation to the isolated chromosomes.