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 retinoblast oma gene is a DNA marker with high informative content frequently used for linkage analysis of familial retinoblastoma. We identified an unreported Dd e I restriction fragment length polymorphism close to the polymorphic Xba I recognition site that interferes with the SSCP analysis of the PR0.6 regio n. We have named this new polymorphism RB1.17. Under most electrophoresis c onditions, the single strand conformations reflect the Dde I genotype rathe r than that of Xba I. The chromosomal localization allele frequencies, inhe ritance and PCR-bused detection of the Dde I RFLP which is useful for linka ge analysis itself are reported.