NCIt definition : Human TPMT*V2 allele is a variant form of the TPMT Gene (TPMT Family), located at
chromosome 6p22.3, which encodes Thiopurine S-Methyltransferase. Some TPMT alleles
contain variable numbers of 17/18 bp tandem repeats (VNTR), within the GC-rich 5'-flanking
TPMT promoter region that modulate the level of TPMT enzyme activity (to a smaller
extent than ORF-based SNP effects). TPMT*V2 contains 2 VNTR. A decrease in gene expression
is seen with increasing repeat numbers.;