A, Location of mtDNA CR mutations in 21 esophageal cancer cases. 7/21 cases demonstrated CR mutations and a vertical bar indicates position within the region. In total, 31 mutations are indicated. Numbers below the bar refer to the standard mtDNA genome position numbering system. B, DNA sequencing electropherograms showing a heteroplasmy present at position 16164 in the blood DNA from case 21. Although a preponderance of G was found, a clear minority of the sequence was A as seen in the tumor DNA. C, 1% agarose gel from the Mitin2/ Mitout2 assay for the 4977 bp common deletion. AN refers to adjacent normal tissue and T to tumor tissue. A very faint band was present in the tumor sample from case 19.