Allozymes
Allozymes are allelic variants of enzymes encoded by structural genes. Enzymes are proteins consisting of amino acids, some of which are electrically charged. As a result, enzymes have a net electric charge, based on the stretch of amino acids comprising the protein. When due to mutation an amino acid has been replaced, the net electric charge of the protein may have been altered. Because changes in electric charge affect the migration rate of proteins in an electric field, allelic variation can be detected by gel-electrophoresis and subsequent specific enzymatic staining. Per enzyme usually two or more loci can be distinguished that have been termed isoloci. Therefore, allozyme variation is also referred to as isozyme variation. Allozymes have been applied in many population genetic issues, including mating structure, (sub)population structure and population divergence. The main drawback of allozymes is their low abundance and low level of polymorphism. Allozymes are particularly useful at the level of conspecific populations and closely related species
Advantages
| No DNA extraction involved |
| No primers or probes required |
| Quick and easy to assay |
| Low costs involved |
| Zymograms can be interpreted in terms of loci and alleles |
| Codominance of alleles |
| High reproducibility |
| Low abundance |
| Low level of polymorphism |
| Zymograms sometimes difficult to interpret due to complex banding profiles arising from polyploidy or duplicate genes and the formation of intergenic heterodimers |
| Proteins with identical electrophoretic mobility (co-migration) may not be homologous |
| Selective neutrality dubious |
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