Gene, genetics and genetic medicines in gastroenterology: Current status and its future

Table 2 Different genetic pathway disorders, its mechanism of action in gastrointestinal tract

Genetic pathway disorder	Mechanism	Examples
Monogenic disorders	Mutations in a single gene that often follow Mendelian inheritance patterns	Hereditary hemochromatosis (HFE gene), Wilson disease (ATP7B gene), alpha-1 antitrypsin deficiency
Polygenic and multifactorial disorders	Involve multiple genes and environmental interactions	Inflammatory bowel disease (over 200 loci have been identified), celiac disease (HLA-DQ2 and HLA-DQ8)
Cancer predisposition syndromes	Inherited mutations in tumor suppressor genes or DNA repair genes increase GI cancer risk	Lynch syndrome (HNPCC) (MLH1, MSH2), familial adenomatous polyposis (APC) gene
Mosaicism	Two or more genetically distinct cell populations within the same individual, derived from a single zygote	Mosaic APC gene mutations may cause attenuated forms of FAP. Very early changes in IBD

GI: Gastrointestinal; FAP: Familial adenomatous polyposis; HNPCC: Hereditary non-polyposis colorectal cancer; IBD: Inflammatory bowel disease.