Obligate Paternal Allele
Definition
The allele in the child's genotype that did not come from the mother and therefore must have come from the biological father.
- Field
- Disputed paternity/maternity testing
- Method
- Subtract maternal alleles from child's genotype
- Remaining allele
- Must have come from the biological father
- Jurisdiction context
- Used in Indian forensic paternity testing
Common questions
What happens when the mother's genotype is not available for comparison?+
Without a maternal sample, the obligate paternal allele cannot be isolated with certainty at loci where the child is heterozygous, since either allele could theoretically have come from either parent. Motherless paternity testing relies instead on population-based statistics and typically requires more loci to reach a comparable confidence level.
How does a mutation at one locus affect an obligate paternal allele analysis?+
A single-locus mismatch, where the alleged father lacks the expected obligate allele at just one marker while matching at all others, is usually treated as a possible germline mutation rather than an exclusion, since STR mutation rates, though low, are well documented and accounted for in standard paternity index calculations.
Is identifying the obligate paternal allele sufficient on its own to confirm paternity?+
No, matching the obligate allele at one or a few loci only fails to exclude the alleged father. Confirmation requires matching across a validated panel of loci and calculating a paternity index and combined probability of paternity, since a random unrelated man can also carry a matching allele by chance at any single locus.
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...
- Mutation Rate
- 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...
- 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....