[Karyotype in GPG bands: description of a elementaly technique for routine (author's transl)].

A new technic for banded chromosomes, with similar results (100%) to those obtained with chromatids modification by trypsin (G bands), is described. The key consists in Pyronin addition (20 mg.%) to distilled water at hypotonic shock, following then a standard karyotype technic assayed with micro-method, reaching banding after Giemsa tinction at 3% in 6.7 phosphate pH. Its interest radicates in chromosome modification in vivo, simplicity, fiability (80% of excellent results) and reproductibility, allowing any cytogenetic laboratory a routine obtention of G bands in only four days.