«Now we are closer to understanding why patients with the exact same genetic mutation in the cystic fibrosis gene have such widely varying manifestations of lung disease, and closer to finding new therapies.» (news.unchealthcare.org)
The best known example is an imprinted locus in chromosome 15, where the exact same genetic mutations cause either the Prader - Willi syndrome if the mutation comes from the mother, or the Angelman syndrome if it comes from the father — with essentially opposite sets of symptoms. (tllab.org)
You might ask: if the mild form and the severe form of CEA / CH disease are caused by the exact same genetic mutation, why do some dogs have only mild disease while others have severe disease? (optigen.com)