Inheritance pattern requiring the influence of a few (two or three) genes. Previously, diseases regarded as monogenic have in recent years been revealed as the product of by an additional gene or genes, and such diseases have been now classified as ‘oligogenic’ rather than ‘polygenic’, as they involve a relatively smaller number of genes. One example is cystic fibrosis, which has for years been regarded as as a single gene disease associated with recessive mutations in the CFTR (Cystic fibrosis conductance regulator) gene. However, further studies of CFTR carried out in more diverse and larger populations have shown that mutations in additional genes could be implicated in modulating the severity of the disease. Thus, diseases stemming from a single gene, with further investigation can reveal a more complex scenario with the identification of additional modulating (or causative) genes. Autism may also be a case important involving oligogenic inheritance together with major or epigenetic contributions.
See Autism, Epigenetics, Gene, Hereditary, Heritability, Mutation (biology), Polygenic mode of inheritance