Fluorescence of Giemsa and related stains: The CF banding of chromosomes
Since the introduction by Caspersson et al. (1970) of the quinacrine fluorescence method for the identification of human chromosomes, several Giemsa staining techniques have been developed for karyotype analysis. A denser staining of centromere regions of chromosomes was noted after in situ hybridization of mouse chromosomes with satellite DNA, followed by Giemsa staining. Numerous modifications were subsequently reported, all producing densely stained regions of one or both chromosome arms close to the centromere. All these procedures are currently referred to as C-banding. The hematological stains Giemsa and Leishman, which are widely used to demonstrate banding in chromosomes, are extremely heterogenous mixtures. They consist mainly of four dyes, methylene blue, Azure A, Azure B, and eosin Y are not considered to be fluorescent under ultraviolet light. In this report a new microscopic technique is described which allows consecutive fluorescence and bright-field observation of hematological stains. The proposed nomenclature for the striking fluorescence of the Giemsa-stained centromere regions of chromosomes is CF-banding. The main advantage of CF-banding over bright-field is that the C-band polymorphisms are better defined. This is especially an advantage in the identification of C-band chromosome polymorphisms in amniotic fluid cultures. Chromosomes from paternal origin in female fetal chromosomes can be identified more accurately. Furthermore, the fluorescence of the CF-method has a high degree of irradiation resistance, and slides can be stored and re-used.