Mutation Rate
Definition
STR loci mutate at roughly 0.001 to 0.005 per generation. A single one-step mismatch is typically scored as a possible mutation, not an exclusion.
- Typical range
- 0.001 to 0.005 per generation
- Applies to
- STR loci
- Single mismatch scoring
- Treated as possible mutation, not exclusion
- Field
- Paternity and kinship DNA testing
Common questions
Why does a single-locus mismatch not automatically exclude a claimed father?+
Given the known per-generation mutation rate at STR loci, a lab expects to see occasional single-step mismatches even in true biological relationships, so protocols require testing additional loci before an exclusion is called on the strength of just one mismatch.
How many mismatched loci typically does confirm an exclusion?+
Practice varies by lab and kit, but two or more independent mismatches across different loci is generally treated as strong exclusionary evidence, since the chance of multiple coincidental mutations in one comparison is very low.
Related terms
- Combined Paternity Index (CPI)
- The product of all individual paternity indices across all marker systems tested. Assumes independence of the marker systems. The CPI is a...
- Deficient Paternity Test
- Paternity inferred from the alleged father's relatives (grandparents, siblings) when the alleged father himself is unavailable or deceased.
- Exclusion
- The categorical conclusion that one or more examined features are clearly inconsistent in a way that cannot be explained by projection angle,...
- Inclusion
- All obligate alleles are accounted for. Inclusion is probabilistic, never absolute, and is reported as a CPI plus probability of paternity.
- Motherless Paternity Test
- Paternity analysis where the mother's sample is unavailable. CPI thresholds are raised because the obligate paternal allele cannot be inferred from the...
- Obligate Paternal Allele
- The allele in the child's genotype that did not come from the mother and therefore must have come from the biological father.
- Paternity Index (PI)
- A likelihood ratio that compares the probability of the observed serological profile if the alleged father is the biological father to the...
- Presumption of Legitimacy
- Statutory presumption that a child born during the continuance of a valid marriage is the legitimate child of the husband. Rebuttable only...
- Probability of Paternity (W)
- The posterior probability that the alleged father is the biological father, calculated from the CPI and a prior probability using Bayes' theorem....