Development of a High-Throughput Method to Isolate Sperm DNA in Sexual Assault Cases

摘要

With the large number of sexual assault cases, the need for a fast and efficient method to process the more than 500,000 reported backlogged evidentiary cases is critical: (1) Currently, the Federal Bureau of Investigations national CODIS (Combined DNA Index System) database contains over 3 million searchable profiles, which can be queried against evidentiary DNA profiles to identify rape suspects; (2) In addition, the number of profiles within CODIS is quickly increasing. Following the approval of the Sexual Assault DNA Backlog Reduction Act of 2002, the major push to eliminate the large number of unprocessed rape kits began with the eventual goal of analyzing all backlogged samples; (3) However, the processing of evidentiary swabs from these rape kits is labor intensive and the development of a more automatable method is highly desirable; and (4) The standard technique for processing semen stains or swabs is known as differential extraction. Typically, this is accomplished by first digesting the epithelial cells in a Proteinase K solution and then separating the digested cells from the intact sperm through centrifugation. The pellet is then resuspended and washed a number of times before being digested with a reducing agent, such as DTT, which breaks the sperm heads, releasing its DNA into solution. This is then followed by standard phenol-chloroform extraction to purify the DNA.