Allozyme variation is an indication of genetic variation. Some amino acid substitutions do not produce different electromorphs. So the number of alleles at each locus is greatly underestimated. For example, at the esterase- 5 locus of Drosophila pseudoobscura the original techniques detected 12 different alleles, but 41 alleles have now been identified. The genetic structure of populations is described using gene frequency and genotypic frequency .
Gene frequencies describe the genetic variation in the entire gene pool.
Genotypic frequencies describe how that variation is organized into genotypes. For each genotype, then, its contribution of a particular allele to the gene pool is its relative genotypic frequency times the probability of producing the allele . The frequencies represent probabilities of occurrence of the respective alleles in the gene pool. Also, any inclusive set of probabilities must total 1.00. Thus, p is the fraction of A alleles in the population, and q is the fraction of a alleles.