Representative examples of mutations detected in microsatellites at gene coding regions. Case numbers are shown above each matching normal (N) and tumor (T) DNA pairs. Arrows indicate the abnormal bands. Note that we have not considered mutated samples where abnormal bands were very faint (like in the BLM and BAX genes of tumor sample 30P). Because of the tendency of Taq polymerase to add an extra nucleotide at the end of the synthesized DNA fragments, PCR products appear sometimes as double bands. With the exception of BAX frameshift in tumor 69R, no other mutation appears to be homozygous. However, by knowing the ratio of malignant cells in tumor sample, we have previously indicated that the BLM mutation in tumor 69R is also homozygous .