R-banding of human chromosomes by heat denaturation and Giemsa staining after amethopterin-synchronization.

Human late prophase to late metaphase chromosomes were prepared after amethopterin cell synchronization. R-banding was produced by heat denaturation followed by Giemsa staining (RHG). Haploid sets of prophase chromosomes contain approximately 850 bands. Sequences of chromosomes of different degrees of condensation are presented; their analysis provides helpful information to identify the elongated chromosomes and to follow band subdivision. The heat denaturation technique is free from most of the disadvantages encountered with R-banding by 5-bromodeoxyuridine incorporation. Giemsa stained R-bands produced by heat denaturation on prophase and prometaphase chromosomes are useful to analyse the numerous chromosome anomalies involving R-bands. In conjunction with G-banding, it is also important to compare adequately the positive and negative regions of each chromosome to define the anomalies with precision.