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Identification and Separation of Evidence Mixtures Using SNP-Based FISH Techniques and Laser Microdissection

NCJ Number
Date Published
July 2012
87 pages
This study examined the feasibility of separating cellular mixtures of the same morphology and gender by developing fluorescence in situ hybridization(FISH) probes based on human genetic single nucleotide polymorphisms (SNPs).
Findings of this research indicated that SNPs are not ideal targets for forensic FISH probing. Probe signals specific to the desired SNP were not detected. It is unknown if this was caused by the specificity of the probe hybridization or the sensitivity of the detection protocols; either is a plausible explanation for the lack of signals. Failure to successfully hybridize to the target sequence and successful hybridization with insufficient detection sensitivity would both produce negative results. Unsuccessful hybridization can be addressed by redesigning the probe or optimizing the hybridization conditions; however, it can be challenging and time consuming to identify the cause of the issue. Examination of alternative RCA techniques may improve the detection sensitivity; however, the alternative RCA techniques may not possess the efficiency necessary for forensic use. It has been reported that RCA is successful in only 20 percent to 55 percent of interphase nuclei targets. For example, if 200 cells are present on a slide, as few as 40 would generate signals. Cells that are not successfully identified with FISH probing cannot be collected for further analysis and key evidence material may be left on the slide. Based on these results, it is recommended to focus future efforts on genetic marker systems that consist of larger genetic differences. Tables, figures, and references

Date Published: July 1, 2012