Molecular analysis of the p53 and p21 genes. Top (left): SSCP analysis of the p53 gene (exon 7). Tumor identification numbers are given on the top of each lane. Cases N612, N519, and N521 show an abnormal migration pattern; (right) sequence analysis of case N612, showing the presence of a G to A transition at codon 248. Bottom (left): SSCP analysis of the p21 gene (exon 2). Cases F2, F10, N613, and N522 show a band shift. This was due to a C to T polymorphism at codon 22 for case F2 (sequence analysis on the right), a C to A polymorphism at codon 31 for cases F10 and N522, and to a C to T somatic mutation at codon 20 for case N613.