DNA analysis is widely applied in solving forensic cases, especially Short Tandem Repat (STR) because of its advantages. In identifying the individual, the National Police compared the individual's DNA with that of his parents. Each anal has a pair of DNA fragments of which half are inherited by the father and the remainder by the mother according to Mendel's Law of Segregation. In this study, we compared DNA typing between the child and the mother with the help of PCR extracted by the Chelex method to find the mother fragment and obtain the father fragment. A child is the biological child of the alleged father if he or she has less than 2 exclusion STR loci. The results of this study revealed that all paternal fragments from the child were identical to the DNA fragments of the alleged father, except for one locus, namely CSF1PO which had a mutation. Mutations in the STR locus lower the paternity index, although it can still be concluded that the child is the biological child of the alleged father.   Keywords: Paternity Test, DNA, STR, Mutation

Background: The most common problem in forensic personal identification, particularly in paternity tests, is the availability of information originating from a mother or a father that can be used as a comparison in the forensic DNA examination process. The use of sibling analysis in paternity tests is still not widely known. Materials and methods: The respondents of this study were 25 families of the Madurese population with 6, 9, and 10 sibling pairs categorized as female-female, male-male, and male-female siblings. The kinship relationship was analyzed by using 13 STR CODIS loci technique (TPOX, D3S1358, FGA, D5S818, CSFIPO, D7S820, D8S1179, THOI, vWA, D13S317, D16S539, D18S51, D21S11), and Amelogenin (Amel) x: 106bp,y: 112bp). Results: The results of DNA contents and purity examination of the extracted DNA sample showed that the average value of DNA contents was 675±5.35 ng/μL with a purity range of 1.05-1.86. The findings proved that the male-male siblings of the Madurese population had the highest allele sharing percentage at the loci of D13S317, D16S539, and D21S11. The highest allele sharing percentage for female-female siblings was at the loci of TPOX and D21S11. Meanwhile, the male-female siblings had the highest allele sharing percentage at the loci of TPOX, D5S818, vWA, D7S820, THO1, vWA, and D13S317. Conclusion: The main STR loci recommended in the male-female siblings of Madurese population identification are TPOX, D13S317, and D21S11.