DPYD enzyme activity and chemotherapeutic toxicity of 5-FU: results from genotyping study on 75 gastric carcinoma and colon carcinoma patients; Med Oncol; 2007; 24(2):251-8. Glossary: Locus (plural loci): the specific location of a gene or DNA sequence on a chromosome, (e.g.; 8p21.1 is the p21.1 region on Chromosome 8). Gene :