Short tandem repeat-based identification of individuals and parents

Estimation of short tandem repeat (STR) multilocus genotype frequencies for the identification of individuals and estimation of allele frequencies for parentage assignment both depend on (a) testing a lot of loci, (b) high le vels of polymorphism at each locus tested, and (c) independence among allel es. Independence is critical, because the estimation of multilocus genotype and gamete frequencies is based on multiplying individual allele frequenci es to produce a composite frequency estimate. Independence among alleles at a locus is known as Hardy-Weinberg equilibrium, whereas allelic independen ce between loci is known as linkage equilibrium. The frequency at which ind ividual identification may be declared is a matter of opinion, as there is no scientific way to specify certainty based on frequency estimates. Simila rly absolute assignment of parentage is impossible in theory; in practice i t is more difficult than individual identification, because only half as mu ch information is available (gamete vs genotype frequency) and because muta tion may confound parentage analysis.