Abstract: Objective To investigate the application of ITO method and discriminant functions method in full sibling and half sibling identification. Methods Five hundred pairs of full siblings(FS), 50 pairs of half siblings(HS) and 500 pairs of unrelated individuals(UR) were genotyped by PowerPlexTM 16 system. Full sibling index(FSI), half sibling index(HSI) and the FSI∶HSI ratio were calculated with ITO method. Allelic matching of each pair of the three groups was compared. The locus numbers of no-allele sharing (x0), half-allele sharing(x1) and two-alleles sharing(x2) were calculated, respectively. The discriminant functions about full-siblings, half-siblings and unrelated individuals(UR) were established by SPSS 13.0 statistical software. Results (1) Regard FSI≥19 or FSI<1 as the standard of distinguishing full sibling from unrelated individual, the alternate correct percentage was 96.4%. Regard HSI≥19 or HSI<1 as the standard of distinguishing half sibling from unrelated individual, the alternate correct percentage was 85.3%. Regard FSI∶HSI≥1 or FSI∶HSI<1 as the standard of distinguishing full sibling from half sibling, the alternate correct percentage was 87.5%. (2) Four groups of discriminant functions were established. The alternate correct percentage of these discriminant functions were 84.4%-97.7%, with the highest one in full sibshipunrelated individual group. Conclusion Both ITO method and discriminant functions method are efficient in identification of full sibling or half sibling.

Key words: forensic genetics, sibling relations, short tandem repeat, discriminant analysis, ITO method