Typically in the human genome a small amount of allele variants account for ~75% of the mutations found at a particular locus within a population.
These genes display allelic heterogeneity at their loci and are responsible for distinct disease phenotypes.
[4] The human gene for the HGD nucleotide sequence shows a number of AKU-causing allelic mutations.
A few known alleles have an indirect effect on protein function by causing misfolding and disrupt the proper assembly of the enzyme complex.
Alkaptunoria is considered to be a classic example of allelic heterogeneity showing a single variant in the human phenotype.