DNA testing
A paternity trio consists of DNA samples from a child (C), a mother (M), and an alleged father (AF). Deficient paternity testing can be performed with just the C and AF samples but will not be as statistically significant without the mother’s DNA profile to help ascertain the father’s obligate alleles. The probability that an alleged father is the actual biological father rather than having the required alleles by coincidence (i.e., that a random man is the true father) is represented as a likelihood ratio known as the paternity index (PI). A maternity index (MI) may be calculated in the same fashion using the allele frequencies for the observed alleles in common between the mother and the child. Toper form parentage analysis, three sets of information are needed: (1) the genotypes for each of the individuals being tested, (2) the relevant allele frequencies for the genetic loci examined, and (3) the appropriate equation from 1 of 21 specific scenarios that depends on the allele combinations present in the tested individuals. The numerator, denominator, and likelihood ratios for each of these 21 scenarios are described more fully in other sources, such as Lucy (2005)
DNA testing