Allele-specific PCR (AS-PCR) amplification of the F200Y single nucleotide polymorphism (SNP) in the isotype 1 β-tubulin gene. PCR products were visualized on a 2.0% agarose gel. Lane M: 100 bp DNA ladder; Lanes 1 and 2: nested PCR products from human samples 4 and 15, respectively; Lanes 3 and 4: AS-PCR products from the same human samples (4 and 15). Lane 5: negative control (AS-PCR), (nuclease-free water).