Null alleles

BeckerK, HohoffC, SuhmittB, Christen HJ, NeubauerBA, Sandrieser T, Becker CM (2006) Identification of the microdeletion breakpoint in a GLRA1 null allele of Turkish hyperekplexia patients. Hum Mutat 27 1061-1062... 

Adenine phosphoribosyltransferase (APRT) deficiency is an inherited disorder of purine metabolism and is inherited in an autosomal recessive manner (K18, V7). This enzyme deficiency results in an inability to salvage the purine base adenine, which is oxidized via the 8-hydroxy intermediate by xanthine oxidase to 2,8-di-hydroxyadenine (2,8-DHA). This produces crystalluria and the possible formation of kidney stones due to the excretion of excessive amounts of this insoluble purine. Type I, with virtually undetectable enzyme activity, found predominantly in Caucasians, is found in homozygotes or compound heterozygotes for null alleles. Type II, with significant APRT activity, found only in Japan, is related to a missense mu-... 

It is clear from family studies that apo(a) gene polymorphism is a consequence of the autosomal codominant Mendelian inheritance of multiple alleles operating at a single chromosomal locus (G7, U4, U6). In families where this simple inheritance pattern was not followed, the existence of a null allele has been postulated (U4, U6). A null allele frequency of 6% was estimated for the subjects... 

If the enzyme is subject to genetic polymorphism with an allele coding for a nonfunctional enzyme, the comparison of the pharmacokinetics of a dmg in subjects homozygous for the null allele to control subjects can yield a value for L-... 

Null alleles that produce no detectable LDL receptor protein. 

The best demonstration that the loss of active normal p53 explains the oncogenic behavior of mutant p53 comes from studies in which a null mutation was introduced into the gene by homologous recombination in murine embryonic stem cells. Mice homozygous for the null allele appear to be normal but are prone to the development of a variety of neoplasms by 6 months of age. These observations suggest that a normal p53 gene is dispensable for embryonic development but that its absence predisposes the animal to neoplastic disease. 

Liu, L. H., Boivin, G. P., Prasad, V., Periasamy, M., and Shull, G. E., 2001, Squamous cell tumors in mice heterozygous for a null allele of Atp2a2, encoding the sarco(endo)plasmic reticulum Ca2+-ATPase isoform 2 Ca2+ pump. J Biol Chem, 276 26737-40. 

Lang T, Klein K, Richter T, Zibat A, Kerb R, Eichelbaum M, Schwab M, Zanger UM. Multiple novel nonsynonymous CYP2B6 gene polymorphisms in Caucasians demonstration of phenotypic null alleles. J Pharmacol Exp Ther 2004 311 34-43. 

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