MSI analysis with quasimonomorphic mononucleotide markers in family 121. 121F: father, peripheral leukocytes; 121M: mother, peripheral leukocytes; 121: proband, glioblastoma; 121S-bl: sister, peripheral leukocytes; 121S-nm: sister, normal intestinal mucosa; 121S-t: sister, colon cancer. Numbers at the bottom of each electropherogram indicate size (in bp).