A combined banding method that allows the reliable identification of chromosomes as well as differentiation of AT- and GC-rich heterochromatin.

Сonstitutive heterochromatin areas are revealed by differential staining as C-positive chromosomal regions. These C-positive bands may greatly vary by location, size, and nucleotide composition. CBG-banding is the most commonly used method to detect structural heterochromatin in animals. The difficulty in identification of individual chromosomes represents an unresolved problem of this method as the body of the chromosome is stained uniformly and does not have banding pattern beyond C-bands. Here, we present the method that we called CDAG for sequential heterochromatin staining after differential GTG-banding. The method uses G-banding followed by heat denaturation in the presence of formamide with consecutive fluorochrome staining. The new technique is valid for the concurrent revealing of heterochromatin position due to differential banding of chromosomes and heterochromatin composition (AT-/GC-rich) in animal karyotyping.