Applications Of STR Loci In The Male Sibling Parentage And Genetic Polymorphism Of Y-STR In Han Population In Henan

Short tandem repeats(STR) are called microsatellite DNA, which account for 5% in eukaryotic genome. Core sequences of them consist of 2～6 base pairs, which are lined up repeatedly in length. In general, a core sequence embraces 1～4 base pairs, and the products of PCR are usually less than 400 bp. The number of repeat in core sequences is variable in terms of different people, therefore STR form their own polymorphisms and this significant variety is also shown in different nations as well as groups of people. Because of their excellent features such as high polymorphisms,extensive distribution and relatively steady heredity based on Mondel codominant inheritance, STR loci are identified as ideal genetic markers in paternity test and personal identification.Y-STR is a sort of short tandem repeats in Y chromosome which contains two different genetic functional regions: pseudo autosomal-region(PAR) and sex-determining region of Y chromosome(SRY). Y-STR loci never occur recombination during meiosis, and they can be passed to their offspring steadily, so they are meaningful markers to identify paternity, male sibling and male collateral relatives.In kindred analysis, genetic information of parents can not be obtained possibly for some reasons. According to this situation, full sibling test is necessary. Even autosomal STR loci in great numbers are applied to conduct a justification, sometimes results still have higher rate of errors. If Y-STR loci are merely applied to, results are not ideal either, due to limited number of loci and relatirely lower polymorphism. Because of lacking both accurate basis and sufficient information, the number of institutions that are able to carry out the full sibling test is less, which cannot satisfy the need of our society.We choose 7 Y-STR(DYS19,DYS385,DYS390,A_7.1,H₄,DYS389 I,DYS389II) in sex-determining region of Y chromosome to investigate polymorphism of 7 Y-STR loci in Han population in Henan. The 7 Y-STR are combined with 13 autosomal STR loci to ascertain the sibling relationship together. This research we conduct can set up a foundation and offer a convenient,efficient method.Methods:Sibling group: 80 pairs of the siblings who are all volunteers are divided into two parts: a group of male siblings (34pairs) and a group of non-male siblings (46pairs). Control group: 160 unrelated individuals are designed to 80 pairs at random, which include a male group (51 pairs) and a non-male group (29 pairs). We are able to read genotype and analyze polymorphism of the 7 Y-STR loci and their haplotype by PCR-STR as well as sliver-dyed. Using autosomal STR and combining them with Y-STR, we compared the rates of identification. The number of the 20 autosmal STR loci of the entirely-same, the half-same, the entirely-different is counted. X2 test is taken to compare the distributing difference of the siblings and the unrelated individuals.Result:1. As to 102 unrelated male individuals of Han population in Henan, there are 5 alleles observed at DYS19 locus, DYS389I locus respectively; 6 alleles at DYS390 locus and A_7.1 locus respectively, 7 alleles at DYS389II, 38 haplotype at DYS385. Gene diversity of 7 Y-STR (DYS19, DYS389I, DYS389II, DYS390, A_7.1, H₄, and DYS385) is 0.754611, 0.635799, 0.755491, 0.672297, 0.681229, 0.638614, and 0.967779 respectively. 99 haplotypes are found in 7 Y-STR loci, in which 97 haplotypes only occur once, the other haplotypes occur twice and three times respectively. The calculated haplotypes diversity is 0.999233. Two pairs from different pedigree in the group of male siblings have the same haplotypes; five individuals in male group have the same haplotypes.2. When 20 autosomal STR are used to identify 80 pairs of the siblings and 80 pairs of unrelated individuals, it shows that pairs are siblings when the locus number of the entirely-different is not more than 2 or that of the entirely-same is not less than 7. And pairs are unrelated individuals when the locus number of the entirely-different is not less than 8 or that of the entirely-same is not more than 2. According to this standard, 23,25 pairs cannot be judged in the group of siblings and the control group, including 11,12 pairs in the group of male siblings and male group. 85 pairs are in the group of male siblings and male group. In two groups, there are 62 pairs which can be justified and 23 pairs which cannot be justified.The 7 Y-STR are combined with 13 autosomal STR loci to identified the group of siblings and control group. As to the 13 autosomal STR loci, it shows that pairs are siblings when the locus number of the entirely-different is not more than 1 or that of the entirely-same is not less than 5. And pairs are unrelated individuals when the locus number of the entirely-different is not less than 6 or that of the entirely-same is not more than 0. When individuals have different alleles in two loci of 7 Y-STR, they can be identified as unrelated individuals. If individuals have all the same alleles in 7 Y-STR, it is possible that they're brothers. According to this standard, all persons in the male group can be identified as unrelated individuals. 19 pairs in the group of male siblings can be defined as brothers, and the rest 15 pairs of the group can be viewed as brothers presumably.3. The allele '7' of A7.1 is found first time in Chinese. This allele is so rare that it has been reported scarcely in the world.4. The haplotype with highest frequency of DYS385 is 13-13 in Han population of Henan, which is identical to the northern Han population of China according to documental reports, yet the haplotype with highest frequency of DYS385 is 12-17 in the southern part of China. It indicates that the distribution of DYS385 is different in different regions. Conclusion:1. This research combines autosomal STR with Y-STR to identify siblings' relationship first time. By this method, it can enhance the rate of identification.2. 7 Y-STR loci are great markers for forensic individual identification.3. The distribution of DYS385 is remarkably different between in the northern part and southern part of China.4. The allele '7' of A7.1 is found first time in China. This allele is so rare that it is reported scarcely in the world.