 Gene loss

Gene loss is evolutionary loss or functional inactivation of an inherited gene. A lineage can lose a function that has become unnecessary, obtain its product from a partner, or retain an alternative pathway. Losing a required function can instead be harmful; absence alone does not establish adaptation.

Comparative evidence must distinguish a true loss from incomplete genome assembly or a sequence that has diverged beyond recognition. Repeated joint losses of EDS1, PAD4 and associated plant immunity components illustrate how loss can reveal dependence within an interacting pathway.^[ref]