an allele which does not amplify during the PCR due to the primer-template mismatch. Indirect evidence of null alleles comes from the departure from the --Hardy-Weinberg equlibrium. Direct detection od alleles is possible through typing of parents and offspring.

The absence of a gene or marker value at a specific location. A null allele may be caused by a deletion of genetic material or the inability to detect a true marker value due to the testing process.

An allele whose effect is either an absence of normal gene product at the molecular level or an absence of normal function at the phenotypic level.

A null allele is an allele with the effect of either absence of the gene product at the molecular level, or the absence of function at the phenotypic level.