Characterization of the canine karyotype by counterstain-enhanced chromosome banding.

The application of the counterstain-contrasted fluorescent banding technique to canine chromosomes provided an improved capability to highlight specific heterochromatic regions and to produce well defined banding patterns both on mitotic and meiotic chromosomes. Triple staining with chromomycin A3 - distamycin A - DAPI revealed the occurrence of DA - DAPI positive heterochromatin in chromosomes 33, 36, 37, and 38. Pachytene nuclei present more favourable material for the detection of very small amounts of DA - DAPI material than mitotic division stages. Counterstain-enhanced chromomycin R-banding greatly facilitated chromosome identification. A standard R-band karyotype of Canis familiaris is proposed and described in some detail. DAPI - actinomycin D staining produced a QFH-type banding pattern and enhanced differentiation of some polymorphic regions.