A simple method to sequentially reveal Q- and C-bands on the same metaphase chromosomes

The Q-C staining procedure, i.e., to treat QM stained preparations with a modified ASG method, conveniently provides Q? and C? (instead of the expected G?) bands on the same metaphase chromosomes. This procedure is especially useful for karyological study of heteroploid cells and interspecific cell hybrids in which extensive chromosomal rearrangements and complex karyotypic compositions are present. A few examples of karyological interest are reported. C-bands, which are either Q+ or Q?, can be divided into two to three subsegments in human chromosomes 1, 9, and 16. These subsegments are connected by a Q?/C?element. Interstitial C-bands could have originated mostly from a C-band without the kinetochore or with the“non-functional” kinetochore.“Double Minutes” are of two kinds, Q+/C+ and Q?/C+. Mechanism for the production of C-bands by the Q-C procedure is briefly discussed.