Schematic representation (not to scale) of the approach used for PCR amplification of the human Fas gene. The exon organization of the cDNA and the relationship of the exons to the domain structure of the protein are indicated. LP, leader peptide; CRH, cystein-rich subdomains; TM, transmembrane domain; ST, apoptotic signal transduction domain; NR, negative regulatory domain. (Below) PCR primers used for amplification of the Fas gene and the relative length of PCR products. Primers were designed according to the cDNA sequence reported by Itoh et al.4