Genetic redundancy

Genetic redundancy is seen when a mutation in a gene has little effect on an organism's phenotype because its lost activity is compensated for by the function of a different gene or genetic pathway. In classical Mendelian genetics experiments this manifests as a form of epistasis where the vast majority of the progeny of a dihybrid cross have normal or near normal phenotypes and only the double homozygous recessive genotype shows a severe mutant phenotype.

Genetic redundancy is not associated with gene duplication and redundant genes do not mutate faster than essential genes.