Is It the Right Match?
You found a match between an ivory sample and a tissue sample from a poached elephant in Garamba National Park. This suggests that the ivory sample and the tissue sample came from the same elephant. But how do you know that the ivory did not come from another elephant that by chance has the same genetic profile? You can calculate the probability that two elephants from a given population would share the same genetic profile if you know the relative frequencies of each allele in that population.
When you look at all the alleles for a particular STR across a population of elephants, some alleles are more common than others. The proportion of individuals that carry a particular allele determines that allele's relative frequency. The gel shows the genetic profile of the ivory sample. Next to each allele is the relative frequency of that allele in the elephant populations that the ivory was suspected to have come from. Alleles that are more common (i.e., more individuals have them) have a higher relative frequency.