MTHFR and cardiac arrhythmia: For example, “Cardiovascular Diseases” (P = 0.0034) enriched with genes AGT, NPPA, ACE, NOS3, ADRB1, MTHFR, FBN1 and GATA4. “Heart Failure” (P = 0.0003) and “Cardiomegaly” (P = 0.0003); from Pathological Conditions: “Hypertrophy” (P = 0.0001); from Anatomy MeSH: “Heart” (P = 0.0001), “Cardiovascular System” (P = 0.0002) and “Aorta” (P = 0.0002); and from domain Tissue Type MeSH: “Myocardium” (P = 0.0008) enriched with NPPA, GATA4, AGT, ADRB1, NOS3, ACE and KCNJ11. GeneGO identified an additional term “Cardiac Arrhythmias” (P-FDR = 3.2 x 10−20).