Description
Y-Screening Application
Traditional serology screening of sexual assault samples is laborious and allows limited sensitivity in comparison to male DNA detection by amplification. Using the Casework Direct no-wash protocol, labs can reduce both cost (labor and reagents) as well as the potential DNA loss typically seen in the DNA extraction step. Additionally, conventional screening results offer analysts little predictive power as to what DNA profile may result. Recognizing the limitations and challenges associated with traditional serology methods, new SWGDAM recommendations are now instructing the use of a “Direct to DNA” approach where DNA analysis is performed before serology to maximize the chances of obtaining CODIS eligible profiles. The figure below demonstrates the successful recovery of male DNA from a series of samples that were processed using the Casework Direct System.
Detection of male DNA in semen dilution series. Dilutions of human semen were spotted on cotton swabs. 400µl of Casework Direct Solution was added to the swab placed in a spin basket assembly, incubated at 70°C for 30 minutes and centrifuged at max speed for 5 min to recover the lysate. 2µl of the lysate was used to quantify the amount of human amplifiable DNA using PowerQuant® System and 0.5ng or maximum volume of lysate was used for STR amplification using PowerPlex® Fusion and PowerPlex® Y23 System. The amplified products were electrophoresed on 3130xl using POP4 with 3kV, 5 sec injection and analyzed on GeneMapper® IDv3.2 with an analysis threshold of 50 RFU. The percentage of alleles called is shown on the left axis and the corresponding template amount on the right y-axis. Less than 0.5ng template amount was available for 1:100 and 1:1000 dilution samples. Profiles were called at all dilution except 1:1000 for PowerPlex® Fusion and Y23.
