Null allele
NONFUNCTIONAL ALLELE (A VARIANT OF A GENE) CAUSED BY A GENETIC MUTATION
Null mutation; Null Allele; Null alleles; Null mutant
A null allele is a nonfunctional allele (a variant of a gene) caused by a genetic mutation. Such mutations can cause a complete lack of production of the associated gene product or a product that does not function properly; in either case, the allele may be considered nonfunctional.