Application of ITO Method in Determination of Special Half-Sibling Relationship

Abstract

ObjectiveTo identify whether the relationship between Zhang A, Zhang B, Zhang C and Zhang X is the half-sibling relationship whose mother is sister （hereinafter referred to as the special half-sibling relationship） or the common first cousin relationship and discuss the application of ITO method in discriminating the special kinship.MethodsDNA was extracted from blood stain of four identified individuals, PowerPlex® 21 System and AGCU 21+1 STR kit were used to detect autosomal STR genetic markers. Investigator® Argus X-12 QS kit was used to detect the X chromosome STR genetic markers, the special half-sibling index （SHSI） and first cousin index （FCI） and their likelihood ratio （LR） were calculated by ITO method.ResultsThe LR results of SHSI to FCI, which were calculated based on autosomal STR genotyping and the analysis of X-STR genotyping results suggested that the relationship between Zhang A, Zhang B, Zhang C and Zhang X was inclined to be a special half-sibling relationship.ConclusionFor the identification of special kinship, it is necessary to comprehensively apply various genetic markers according to the case. After the conclusion that shared alleles cannot be excluded from the analysis, ITO method can be further used to establish discriminant assumptions according to the specific case to obtain objective and reliable identification opinions.

Keywords

• forensic genetics
• ito method
• short tandem repeat （str）
• sibling relationship
• likelihood ratio
• half-sibling index
• first cousin index