Quantitative Analysis of Mixed DNA Proportions from Two Donors

The aim of this study is to propose an efficient method for analyzing donor proportions in mixed DNA samples, especially the application of short tandem repeat (STR) data in forensic science. Quantitative analysis of mixed samples often faces the problem of imprecise donor ratios, especially when multiple alleles are present in the sample. In this study, the maximum allele count method was used to calculate the minimum donor number based on the number of superior genes in the locus, and the influence of heterozygote balance on the estimation of mixing proportion was further analyzed. In the experiment, by measuring the heterozygote peak height ratio (PHR) and setting 0.6 as the equilibrium threshold, the analysis results of heterozygote meet the requirements of forensic science. Then, the residual sum of squares (RSS) method was used to optimize the genotypes of the mixed samples, and the mixing ratio was accurately determined by comparing the difference between the predicted peak height and the actual peak height. The results show that the proposed method has high accuracy when dealing with mixed samples, especially in complex samples, it can effectively determine the contribution proportion of different donors. By establishing a linear model and fitting algorithm, this study not only provides accurate technical support for forensic science, but also provides a quantitative analysis method for mixed DNA sample analysis.