The Application of 'Gentle'Differential Lysis Method in the Identification of Cold Rape Cases
In this paper,we summarized a"gentle"differential lysis method by sharing the experimental process and successful experiences of a sexual assault cold case.This method can provide a new solution for handling old mixed stains.The biological sample is the long underwear wom by the victim at the time of the crime.Firstly,we got a positive PSA result of the mixed stains,and then we obtained great mixed DNA profiles with males and females using the one-step lysis method.When we tried the traditional differential lysis method to get a complete single male DNA profile,the result was disappointing because we only met female DNA profiles of the supernatant and the precipitation had nothing.By many tests,we modified the lysis conditions of the female cells to 1mL of lysisbuffer,37 ℃,20 min and the working concentration of protein's K(Protease K,PK)is 50 μg/mL,after lysis,wash the precipitation once time by 1 mL ddH2O.Finally,we successfully obtained single DNA profiles of both female and male.Subsequently,further testing of this method was carried out utilizing simulated mixed stains from known male and female samples,this method had a good efficiency when the ratio of male to female was below 1:40 in mixed stains.At the end,we discuss the relevant factors affecting the quality of sperm DNA profiling results and the considerations for applying this method in practice.
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