Restriction map of the 630-bp PCR products (top). The arrow indicates the position of the restriction site for MaeIII endonuclease. The length of the restriction fragments is shown above. RFLP analysis of PCR-amplified genomic DNA derived from peripheral blood cells (PBL) of Sit^a-phenotyped individuals. DNA fragments were analyzed on 1.6% agarose gel stained with ethidium bromide (bottom). The undigested 630-bp PCR product is shown in lane 1. Lanes 2 and 3 represent the analysis of MaeIII-digested PCR product derived from DNA of a Sit^a (+) heterozygous individual and a Sit^a (−) individual, respectively. Lane 4, DNA size standards (pBR328 DNA.BglI + pBR328 DNA.HinfI).