Hardy-Weinberg Equilibrium (HWE)
Definition
The expected genotype frequency in a large, randomly mating population with no selection, mutation, or migration. Under HWE, the frequency of a heterozygote Aa is 2pq and a homozygote AA is p-squared, where p and q are allele frequencies. The product rule assumes HWE holds at each locus; the theta correction relaxes this assumption for substructured populations.
Related terms
- Likelihood Ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- Product Rule
- The rule that, under independence, the joint probability of a multi-locus genotype equals the product of the individual locus genotype frequencies. Used...
- Prosecutor's Fallacy
- The error of treating the RMP (or its reciprocal) as the probability that the defendant is innocent, or as the probability that...
- Random Match Probability (RMP)
- The probability that a randomly chosen unrelated person from the relevant population would match the evidence profile by chance. A very small...
- Theta (FST) Correction
- A correction factor applied to allele frequency estimates to account for population sub-structure (the tendency for allele frequencies to differ between sub-populations)....
- Allele Frequency
- The proportion of a specific allele variant at a given genetic locus in a defined population. Forensic match probability calculations multiply the...
- Defence Attorney's Fallacy
- The incorrect argument that a large global or national population means many unrelated individuals could share the profile, while ignoring the geographic...
- ENFSI DNA Working Group
- The European Network of Forensic Science Institutes DNA Working Group. Coordinates European forensic DNA standards, including the evaluative reporting guidelines adopted by...
- 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...
- Population Substructure
- The condition in which allele frequencies differ systematically between subgroups within a nominally single population. Substructure means that individuals within a subgroup...
- Prior Odds
- The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis before the forensic evidence in question...
- 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...
Explained in these topics
- DNA Match Probability CalculationThe expected genotype frequency in a large, randomly mating population with no selection, mutation, or migration. Under HWE, the frequency of a heterozygote Aa...
- Population Databases for Forensic StatisticsThe expected genotype frequency distribution in a population that is randomly mating, large, and free from selection, mutation, and migration at a given locus....
- Allele Frequencies, Random Match Probability and the Likelihood RatioThe prediction that genotype frequencies in a large, randomly mating population equal the products of allele frequencies. Underpins the computation of genotype...