Molecular diagnosis and treatment of drug-resistant hepatitis B virus

Figure 2 Schematic diagram of the restriction fragment mass polymorphism genotyping strategy. Polymerase chain reaction is performed with primers designed to introduce a type IIS restriction endonuclease recognition sequence (FokI) ahead of the genotype-specific motifs upon amplification. The enzymatic cleavage of the products leads to excision of multiple oligonucleotide fragments representing the motifs shown in capital letters, and then the masses of the resulting oligonucleotide fragments are examined by MALDI-TOF MS. Cleavage sites of FokI and BstF5I, an isoschizomer of FokI, are indicated by filled and blank arrows, respectively, and recognition sites for both restriction endonucleases are specified by the shaded bars.