Identification of heterogeneity within the tumor cell population. Plotting a chromosome highlighted against the whole sample allows discovery of genomic regions with heterogeneity within the tumor cell population, shown here on two regions in lung cancer cell line H1395. The arrows mark the chromosomal segments and their respective positions in the scatter plots. (a) On chromosome 1, most of the q arm has loss of heterozygosity and an average of about 3.5 copies. The high-copy segment near the centromere is not visible in this scatter plot. (b) The end of 10q is seen between the clusters for normal ploidy and deletion, indicating deletion only in part of the cell population.