Korean J Leg Med.  2013 May;37(2):57-65. 10.7580/kjlm.2013.37.2.57.

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

  • 1Department of Forensic Medicine, Yonsei University College of Medicine, Seoul, Korea. kjshin@yuhs.ac
  • 2DNA Analysis Laboratory, DNA Forensic Division, Supreme Prosecutors' Office, Seoul, Korea.


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.


STR; Kinship index; Simulation; Familial searching; Koreans

MeSH Terms

Asian Continental Ancestry Group
Discrimination (Psychology)
Gene Frequency
Microsatellite Repeats


  • Fig. 1. Virtual pedigree constructed by simulated autosomal STR profiles in this study.

  • Fig. 2. Likelihood ratio distributions for parent/child relationship with 13 (a) and 20 autosomal STR loci (b). Red and orange lines represent related distributions. Blue and skyblue lines indicate unrelated distributions.

  • Fig. 3. Likelihood ratio distributions for full-siblings relationship with 13 (a) and 20 autosomal STR loci (b). Red and orange lines represent related distributions. Blue and skyblue lines indicate unrelated distributions.

  • Fig. 4. Likelihood ratio distributions for uncle/nephew relationship with 13 (a) and 20 autosomal STR loci (b). Red and orange lines represent related distributions. Blue and skyblue lines indicate unrelated distributions.

  • Fig. 5. Likelihood ratio distributions for first cousins relationship with 13 (a) and 20 autosomal STR loci (b). Red and orange lines represent related distributions. Blue and skyblue lines indicate unrelated distributions.

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