null allele

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null allele

A segment of DNA which is not known to encode a protein product.

null allele

a form of a gene whose product is either absent at the molecular level, or is present but has no measurable phenotypic function. For example, in a heterozygote with INCOMPLETE DOMINANCE one gene form is a ‘null allele’ and is inactive, while the other allele is unable to compensate for the null allele and so produces an intermediate phenotype.
References in periodicals archive ?
Two loci (cmrDe2 and cmrDe9) showed significant deviations from H-W expectations, both with deficits of heterozygotes, possibly due to the presence of null alleles or the small sample size (Table 3).
Null alleles were detected in both wild and hatchery Mercenaria mercenaria.
2006) in study of costal cod (Gadus morpha), stated that several factor such as increasing homozigosit, genetic drift, selection, low sample size and null alleles is possibly cause of the Hardy-Weinberg disequilibrium.
The departure of allele frequencies from Hardy-Weinberg expectations at all microsatellite loci used in this study indicated the presence of null alleles (Jones and Arden, 2003).
Analysis with MICRO-CHECKER indicated the possibility of null alleles at one microsatellite (Lca 20) where the probability of deviation from Hardy-Weinberg equilibrium expectations was significant (P=0.009) before Bonferroni correction.
We also selected the more rare SNPs M46V, G99E, K139E, and I391N, described as phenotypic null alleles in Caucasians, and the R140Q SNP that strongly affects enzyme activity (21).
Lines were developed from matings between Asian and North American sources of the Wx null alleles. After the last cross in each pedigree, the brush end of [F.sub.2] plants was stained with a dilute solution of [I.sub.2]KI and the germ end was saved for planting.
Null alleles at microsatellite loci are a general complication for parentage assessments in nature (Callen et al.
The frequency of null alleles varied from -0.0548 to 0.0563 and none of these loci showed evidence of null alleles.
In this case, the nature of the deviations is suggestive of null alleles, as indicated by the MICRO-CHECKER analysis.