PCR-SSCP analysis of the _IIband β₃ genes. PCR amplification products were submitted to SSCP analysis by electrophoresis on the minigels of the PhastSystem apparatus and the migrated products detected by silver staining. (A) Only the amplification product for exon 3 of the β₃ gene of patient A.P. exhibited a different migration profile to the control (C); this corresponded to the HPA-1 genetic determinant, the control being HPA-1a/HPA-1a and the patient being HPA-1a/HPA-1b. For the _IIb gene, three amplification products had different patterns when compared with the control. For amplification product 21, this corresponded to a previously described polymorphism (Noted Del⁺ and Del⁻) in intron 21. Amplification product 26 corresponded to the HPA-3 system, the control being HPA-3a/HPA-3a and the patient being HPA-3a/HPA-3b. (B) SSCP analysis of amplification product 30 of the _IIbgene showed a previously undescribed pattern. Illustrated are the patterns obtained for the patient (A.P.), a control, his father, and his mother. Band a was present for the control and the two parents, band b for A.P. and his mother, and band c for A.P. and his father.