Double minute chromosomes in a lung cancer cell line. A short-segment TAPS scatter plot illustrates the origin of double minute chromosomes (DMs). Lung cancer cell line H1395 has three copies of chromosome arm 11p (blue) and no loss of heterozygosity (LOH). Most of 11q is copy number 2 with LOH (red). The DMs appear as several successive short segments with varying total copy numbers (violet). Their minor allele varies between zero and two copies when the major allele has two copies, and remains at two when the major allele is above two. This suggests that circular DMs originate from the sister chromosome that in most of 11q has been lost. The remaining sister chromosome is duplicated but otherwise unchanged.