ABSTRACT
Cytogenetic analysis of both colchicine-resistant (CLC) panels reveals an increase in the complexity of the karyotype with increasing CLC. Gene amplification was observed at higher levels of CLC associated with recognizable abnormally banding regions or double minute chromosomes. Investigators have described and characterized distinctive chromosomal structures formed early in the amplification of several different amplified genes. The finding of the large extended regions of DNA at the site of the single copy gene in early steps in the process of CLC drug selection appears to be entirely analogous to the examples visualized in early steps of CAD and dihydrofolate reductase amplification. The PGY cDNA probe was tritium-labeled by nick translation to a specific activity of approximately 10 counts per minute per microgram of probe DNA. At the earliest steps of selection in both independent panels, unusual chromosomal structures characteristic of newly amplified PGY DNA were observed linked to the long arm chromosome 1, presumably by a process of interstitial duplication.
