Dde I RFLP may falsify linkage analysis of hereditary retinoblastoma when using SSCP of p88PR0.6 region.

The polymorphic p88PR0.6 locus (Xba I RFLP) in intron 17 of the retinoblastoma gene is a DNA marker with high informative content frequently used for linkage analysis of familial retinoblastoma. We identified an unreported Dde I restriction fragment length polymorphism close to the polymorphic Xba I recognition site that interferes with the SSCP analysis of the PR0.6 region. We have named this new polymorphism RB1.17. Under most electrophoresis conditions, the single strand conformations reflect the Dde I genotype rather than that of Xba I. The chromosomal localization, allele frequencies, inheritance and PCR-based detection of the Dde I RFLP which is useful for linkage analysis itself are reported.