Nullmutattion

Null mutation, also called a null allele, is a genetic change that abolishes the function of a gene product. A null allele can result in no functional protein being produced or in a protein that lacks activity. Null mutations can arise by various molecular mechanisms, including nonsense mutations that create a premature stop codon, frameshift mutations that alter the reading frame, splice-site mutations that prevent proper mRNA processing, large deletions that remove coding sequence, or promoter and regulatory changes that eliminate transcription.

Most null mutations have recessive inheritance, meaning that one normal copy of the gene can compensate in many cases. However, some genes are haploinsufficient, and a single null allele can produce a measurable phenotype. In rare cases, a mutation may act in a dominant-negative manner or have gain-of-function effects, which are not true nulls.

Null mutations are valuable tools in genetics and molecular biology. They are used in knockout models to study gene function, in comparative population genetics to assess essentiality, and in clinical genetics to diagnose diseases caused by loss of gene function. The severity of a null mutation often correlates with the gene's essentiality and the organism's tolerance for reduced gene activity. Detection typically relies on sequencing and functional assays to assess gene expression and activity.