JAK2 exon 19 SNP genotype analysis of V617F mutant alleles. (A) Gel showing AflIII restriction enzyme digest of 14(MM)F + 15R PCR products amplified from 14(MM)F + 20R second-round PCR products that were obtained from 6 ET patients. V617F mutant–positive products remained undigested. Un indicates no restriction enzyme added; WTc, wild-type control. (B) Gel showing BstNI restriction enzyme digest of 18F + 20R PCR products amplified from the same 14(MM)F + 20R second-round PCR products. Exon 19 SNP allele G, but not A, products were digested. Un indicates no restriction enzyme added; Gc, allele G control.