Homogeneously staining chromosome regions and double minutes in a mouse adrenocortical tumor cell line

We have used a number of banding techniques to analyze the chromosomal content of two sublines of the steroid-secreting mouse adrenocortical tumor cell line Y1. One of the sublines contains marker chromosomes with large "homogeneously staining regions" (HSRs). The other subline contains numerous double minutes, but no HSR. The presence of marker chromosomes shared by both sublines indicates their derivation from a common precursor. Both sublines are karyotypically stable, have similar growth rates, and exhibit positive staining for delta 5, 3 beta-hydroxysteroid dehydrogenase.