The metaphase chromosome ultrastructure: I. Acute angle metal deposition technique as an appropriate use of shadow casting in chromosome structure investigation

Abstract The ultrastructure of the metaphase chromosome, isolated by spreading and dried by the critical point method, has been studied by the technique of rotary shadow casting at very acute angles, equivalent to deposition of metal on the specimens at mere grazing incidence. Acute angle deposition visualizes a three-dimensional image of the chromosome periphery and the substructure of the basic chromosome fibre. This paper describes the technical details of acute angle deposition as a particular use of shadow casting. The technique seems to be adequate for the study of the three-dimensional aspects of relatively large subjects and represents an alternative to scanning electron microscopy when the details under study are in the 150 A range.