General Formulas for Calculating Commonly Used Kinship Index / 法医学杂志

OBJECTIVES@#To derive general formulas for calculating commonly used kinship index (KI).@*METHODS@#By introducing the Kronecker symbol, the formulas used to calculate the same KI under different genotype combinations were summarized into a unified expression.@*RESULTS@#The general formulas were successfully derived for KI in various case situations, including the paternity index, full sibling index, half sibling index, avuncular index, grandpaternity index, first-cousin index, and second-cousin index between two individuals without or with the mother being involved; grandpaternity index between grandparents and a grandchild without or with the mother being involved; half sibling index between two children with two mothers being involved; full sibling index among three children; and half sibling index among three children with no, one, or two mothers being involved.@*CONCLUSIONS@#The general formulas given in this study simplify the calculation of KIs and facilitate fast and accurate calculation through programming.

Analysis of Trio Half Sibling Testing / 法医学杂志

OBJECTIVES@#To establish an analytical method for half sibling testing involving common three relatives' participation.@*METHODS@#Based on the half sibling testing scenarios with the known biological mother, grandfather or uncle, and two unidentified controversial half siblings participating, two opposing hypotheses were set. Lineage reconstruction according to Mendel's law of heredity was carried out, and the calculation formula of the half sibling kinship index was derived. Verification of actual cases was carried out and the results were compared with duo half sibling testing.@*RESULTS@#In the scenarios of the known biological mother, grandfather and uncle participating in half sibling testing, the kinship calculation formulae of 54, 91 and 99 genotype combinations for kinship index calculation were deduced respectively. The actual cases showed higher kinship indexes in trio half sibling testing compared with duo half sibling testing.@*CONCLUSIONS@#It is beneficial to obtain more genetic information for family reconstruction and improvement of the strength of genetic evidence for half sibling testing by adding known relatives.

Analysis of Kinship Index Distributions in Koreans Using Simulated Autosomal STR Profiles / 대한법의학회지

Kinship testing in forensic casework is largely based on a likelihood ratio (LR) approach with short tandem repeat (STR) markers; however, in order to efficiently identify potential relatives in a specific population, the threshold values for kinship prediction should be determined by analyzing the kinship index distributions of the population in question. In this study, 250,000 DNA profiles were simulated using allele frequencies at 20 autosomal STR loci in Koreans, then the LRs were calculated for true close relatives and unrelated pairs. The LR distributions in related and unrelated pairs under a given relationship were compared in 2 sets of 13 Combined DNA Index System (CODIS) and 20 STR profiles. Using 13 CODIS STRs, true relatives in parent/child and full-sibling relationships were sufficiently discriminated from unrelated pairs with LR thresholds of 1,000 and 100, respectively. However, the CODIS STRs lacked the discriminatory power to differentiate between related and unrelated pairs in uncle/nephew and first cousin relationships due to high false-positive and false-negative rates with a LR threshold of 10. Increasing the number of STR loci to 20 increased discrimination of close relatives, but high false results remained in uncle/nephew and first cousin relationships. The kinship index data from this study will help make decisions on various kinship testing and familial searching in Koreans.

Web-based Y-STR Database for Haplotype Frequency Estimation and Kinship Index Calculation / 대한법의학회지

We developed a web-based Y chromosomal short tandem repeat (Y-STR) database (ySTRmanager, http://ystrmanager.yonsei.ac.kr) to facilitate calculation of Y-STR haplotype frequency estimates for random matches and kinship indices for various relationship levels. The ySTRmanager database provides 3 functions: (i) Y-STR haplotype search, (ii) kinship index calculation, and (iii) user database configuration. The Y-STR haplotype search function allows researchers to retrieve Y-STR haplotypes that meet queried Y-STR allele, Y-haplogroup affiliation, and/or sample information from a selected population in the open database, which consists of 12-17 Y-STR loci. The number of matches in a selected population, haplotype frequency estimator, and detailed results for matched and neighbor haplotypes are displayed as a set of search results. The kinship index calculation function provides kinship indices of 2 input Y-STR haplotypes for the relationship represented by the number of meioses, with consideration of target population and mutation rate of each Y-STR. In addition, ySTRmanager allows registered users to configure their own database to store and analyze Y-STR haplotype and/or mutation rate data. The stored Y-STR data can be used in the search function and in the analysis to obtain forensic statistical values. The ySTRmanager will be a useful system to analyze and manage Y-STR data in the practice of forensic genetics.