High resolution detection of human metaphase chromosomes.

The new generation of field emission in lens scanning electron microscopy with the sample located within the objective lens allows the observation of uncoated biological samples. Here we describe HeLa metaphase chromosomes isolated by two procedures and the localization within these chromosomes of a DNA centromeric probe. Chromosomes isolated in methanol acetic acid show 10 nm fibers organized in a three dimensional network while the structure of chromosomes obtained by the polyamine method's characterized by very dense short protusions of 30-50 nm in thickness. In situ hybridization with a DNA centromeric probe revealed by colloidal gold particles demonstrate that the hybridization occurs at the level of the 10 nm fiber with a high definition in the localization of specific DNA sequences.