Detection and characterization of a new polymorphic marker in exon 13. Upper left, separation by electrophoresis of the PCR product digested with Rsa I. The gel (2% agarose) was run at 70 V for 1 hour. Lane 1, subject heterozygous for the R3 allele and for the frequent R1 allele. Lane 2, subject homozygous for the R2 allele. The restriction map for R2 and R3 alleles is reported below. Upper right, detection of the R3 polymorphism by sequencing. The A/G transition is indicated by the open arrow. Nucleotide numbering according to Jenny et al.3