The effectiveness of using co-dominant polymorphic allelic series for (1) checking pedigrees and (2) distinguishing full-sib pair members.

Formulae express the effectiveness of parentage exclusion tests and differences separating full-sib pairs by compounding genotypic information on discrete examples of co-dominant alleles segregating at gene loci on different autosomes. Such polymorphisms occur among structural genes and polymorphic DNA sequences. Two general formulae state the theoretical effectiveness of using co-dominant alleles for (1) testing parentage and (2) distinguishing sibs. The formula for parentage exclusion tates the probability (PE) that a given series of co-dominant alleles of known frequency should detect a falsely recorded father (or mother). The other formula describes how genetic polymorphism can distinguished closely related individuals. It states the probability (PS) that alleles distinguish the members of full-sib pairs, dizygotic twins and tissue chimeras. To derive the two general formulae, particular formulae were calculated for n = 2, 3 and 4 co-dominant alleles. By increasing the numbers of alleles, the formulae were seen to contain recurrent patterns which were then expressed in the two general formulae for n alleles. Some examples demonstrate applications of the two formulae in problems concerning parentage and sibship.