Mechanisms of Giemsa banding. II. Giemsa components and other variables in G-banding.

We investigated the capability of individual thiazins in Giemsa mixture (methylene blue and azures A, B, and C) and of two related dyes (toluidine blue and thionin) to produce G-banding. We further tested the effects of variations of buffer composition and concentration, dye concentration, and staining time. G-banding was produced by all of the dyes at low concentrations, although differences were noted. Overall, methylene blue and azure B produced the best banding, azures A, C, and toluidine blue produced moderately good banding, and thionin produced poor banding. This order did not appear to be altered essentially by different treatments. The optimal conditions for G-banding for all dyes and treatments included the use of (1) 0.025-0.05 M phosphate buffer, (2) dye concentrations of 0.002%--0.005%, and (3) staining times of 6--15 min.