The Paternity Index (PI) for a genetic polymorphism is a ratio of probabilities which can be used to help determine the conditional probability of whether an alleged father is the actual father of a child.
paternity index =
= (probability of a child's alleles resulting from a mating of the mother and alleged father) / (probability of a child's alleles resulting from a mating of the mother and a random male of the same racial background)
probability of a child's alleles resulting from a mating of the mother and alleged father =
= 0.5 if the father is heterozygous and has a match for the nonmaternal allele in the child
= 1.0 if the father is homozygous and has a match for the nonmaternal allele in the child
= 1.0 if the child is female, the marker is X-linked and the father has a match for the nonmaternal allele in the child
probability of a child's alleles resulting from a mating of the mother and a random male of the same racial background =
= allele frequency in the population
If there is no match between a nonmaternal allele in the child and the alleged father, then the PI = 0.
To read more or access our algorithms and calculators, please log in or register.
