Frequency of copy number change. (A) Frequency of gene amplification (black), gain (red), and loss (green) in the 20 GBMs relative to their map position in the EnsEMBL database (calculated as the number of GBMs showing amplified, gained, or lost genes vs. the number of tumors analyzed for each gene). The white vertical bars represent the separation between chromosomes. Only the most representative chromosomes are shown. Map positions for each cDNA clone were obtained from the EnsEMBL database using the IDconverter tool .