Strategy Of Conclusion-Making For Paternity Testing In The Point Of View About Close Relatives

Objective: To research and discuss the strategy of conclusion-making for paternity testing in the point of view about close relatives.Method: The research divided into five parts.1,Investigated a family of four generation including 25 person. Obtain the result of 15 STR loci (CODIS+D2S1338,D19S433) and the proportion of the confusion cases.2,Modified the probability of exclusion by the formula PER=(k₀+k₁)PE, which is the power of relatives in single locus; Calculate the minimal numbers of STR loci by the formula of binomial distribution in the point of view about close relatives;3,Investigated genetic datum of 21 non-CODIS STR loci and combined with 19 STR loci in common use, validated in the typical case.4,Modified the likelihood ratio by the formula LR=k₀+(1-k₀)PI, and associating with typical paternity index (PI_typical ) to generalize the modified coefficient for paternity index in the point of view about close relatives.5,Establish the discrimination function about the number of alleles identical by state though the genotypes of sib pair group and unrelated pair group in 19 STR loci.Results:1,The result of 35 paternity cases of uncle/child pair replace the father/child pair indicated that: If only detecting 15 STR loci, 17% of trio case and 37.5% of duo case may cause confusion.2,Considering the disturbance of close relatives(except full siblings), the emendated PE is as 0.75 times as before. When 0-3 inconsistent STR loci were detected, it is accordingly detected 15, 24, 35 and 43 loci in all for trio testing and detected 21, 34, 48 and 61 loci in all for duo testing.3,Obtained 20 additional STR loci and it has good effect when validated in the typical case combined with 19 STR loci in common use.4,If the number of detected loci is n, it should multiplied the CPI by the emendating coefficient: 0.75^n-m.(Where m is the number of inconsistent loci )5,The numbers of alleles identical by state(S) can evaluate whether two individuals is full sib pair or unrelated pair. The discriminant function in sib group is Lsib =3.3408×S-39.8808; the discriminant function in unrelated individual group is Lunrelated=1.6685×S-10.4679. When the numbers of alleles identical by state is more than 21 or less than 14 in 19 STR loci, posterior probability of a full sib or unrelated individuals is more than 0.9967 or less than 0.9975, respectively. Associating with other rules of genetic, it can distinguish between full siblings and other relationships.Conclusion: In the paternity test, if other relatives replace the real parents, only detected 15 STR loci in common use may cause confusion and fault. If the total number of loci overrun the request in result 2, it can avoid the fault.The method and strategy in this paper can evaluate and avoid the risks of the disturbance of close relatives to a certain extent, and provided evidence for further research.