Likelihood ratio (PI) = X / YX, chance that the Alleged Father could transmit the obligate alleleY, chance that some other man of the same race could have transmitted the alleleX = 1, if father is homozygousX = 0.5, if father is heterozygousFor D18S51, 16 was obligate allele, frequency of 16 = 0.0046PI = X / Y = 0.5 / 0.0046 = 108.696