Sequence analysis of amplification products of exon 13 of the hMSH2 gene in human LBL (A and B). (A) A patient with a heterozygous frameshift mutation resulting from a 1-bp deletion at codon 672-673. (B) A patient with a heterozygous missense C → A mutation at codon 724, displayed in an antisense configuration. The locations of the mutations are indicated with arrows.