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Allelic heterogeneity is the phenomenon in which different mutations at the same locus lead to the same or very similar phenotypes. These allelic variations can arise as a result of natural selection processes, as a result of exogenous mutagens , genetic drift , or genetic migration .
Genetic heterogeneity occurs through the production of single or similar phenotypes through different genetic mechanisms. There are two types of genetic heterogeneity: allelic heterogeneity, which occurs when a similar phenotype is produced by different alleles within the same gene; and locus heterogeneity, which occurs when a similar phenotype is produced by mutations at different loci.
When allelic gene conversion removes the major allele at these sites organisms are likely to experience a mild decline in fitness. Because LOH is much more common than de-novo mutation, and because the fitness consequences are closer to neutrality, this process should drive Muller's ratchet more quickly than de-novo mutations.
In medical genetics, compound heterozygosity is the condition of having two or more heterogeneous recessive alleles at a particular locus that can cause genetic disease in a heterozygous state; that is, an organism is a compound heterozygote when it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be ...
Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion. [1] Gene conversion can be either allelic, meaning that one allele of the same gene replaces another allele, or ectopic, meaning that one paralogous DNA sequence converts another.
Locus heterogeneity should not be confused with allelic heterogeneity, in which a single phenotype can be produced by multiple mutations, all of which are at the same locus on a chromosome. [1] Likewise, it should not be confused with phenotypic heterogeneity , in which different phenotypes arise among organisms with identical genotypes and ...
A genetic or allelic heterogeneous condition is one where the same disease or condition can be caused, or contributed to, by varying different genes or alleles. In clinical trials and statistics the concepts of homogeneous and heterogeneous populations is important. The same applies for epidemiology [citation needed]
In cases of allelic heterogeneity, the MIM number of the entry is followed by a decimal point and a unique 4-digit number specifying the variant. [9] For example, allelic variants in the HBB gene (141900) are numbered 141900.0001 through 141900.0538. [10]