Population substructure
Definition
The condition in which allele frequencies differ systematically between subgroups within a nominally single population. Substructure means that individuals within a subgroup share alleles more often than random mating would predict, which can cause a database to under-estimate or over-estimate match probabilities for members of a specific subgroup.
Related terms
- Allele frequency
- The proportion of a specific allele variant at a given genetic locus in a defined population. Forensic match probability calculations multiply the...
- Hardy-Weinberg equilibrium (HWE)
- The expected genotype frequency in a large, randomly mating population with no selection, mutation, or migration. Under HWE, the frequency of a...
- Minimum allele frequency (minimum frequency ceiling)
- A conservative lower bound applied when an allele is absent or very rare in the database, to prevent an artificially inflated match...
- Reference population database
- A curated collection of allele frequencies or feature measurements from a defined population, used to estimate the probability that a randomly chosen...
- Theta correction (FST or coancestry coefficient)
- A statistical adjustment applied to DNA match probability calculations to account for expected allele-sharing within subpopulations due to substructure. A theta value...
Explained in
- Population Databases for Forensic StatisticsThe condition in which allele frequencies differ systematically between subgroups within a nominally single population. Substructure means that individuals wit...