In humans, simple deficiency of many serpins (e.g., through a null mutation) may result in disease (see Table 1).

SOD2 knockout or null mutations cause growth inhibition on respiratory carbon sources in addition to decreased post-diauxic lifespan.

This protein is considered a crucial component of the axon and presynaptic terminal, its null mutation leading to death within days after birth due to axon pathfinding defects.

Initial studies demonstrated that most SI mutations result in lack of enzyme protein (i.e. null mutation) [ 26 ] .

The recessive form of the disease is caused primarily by null mutations, although amino acid substitutions, splice junction mutations, and missense mutations have also been reported.

Functional null mutations in this gene cause Carney complex (CNC), an autosomal dominant multiple neoplasia syndrome.

Mice with null mutations ("knockouts") in Brn3a die at birth, due to developmental defects in the nucleus ambiguus, which is essential for respiration.

Inner ear defects induced by null mutation of the isk gene.

Clock mutant organisms can either possess a null mutation or an antimorphic allele at the Clock locus that codes for an antagonist to the wild-type protein.

A null mutation in such a gene may be lethal to the embryo and such mutants would be missed in a basic screen.