Bode can supplement conventional STR analysis with Y-STR analysis on forensic casework samples. Under certain circumstances, conventional STR analysis may fail to clearly distinguish the male contributor DNA in a sample. This can occur in the case of a mixture with a major component female STR profile and a few alleles from a male contributor. Y-STR analysis can provide the clarity necessary to render a conclusion regarding the inclusion or exclusion of a specific individual.
Forensic mixtures may contain cell types that cannot be separated using differential extraction techniques (i.e. dried saliva stain on a victim) If the male DNA isolated from the sample is a low-level minor component, Y-STR analysis can provide useful information regarding the identity of potential contributors. Bode has developed a Y-Marker Screen (YMS) assay to screen samples for the presence of male DNA if appropriate. The YMS test is more sensitive than the STR multiplexes used for DNA analysis to ensure that low levels of male component DNA are identified. The YMS test is a simple and efficient way to determine if male DNA is present, if an STR profile can be generated from a sample, and whether Y-STR analysis will be effective.
Y-STR analysis can be used in non-sexual assault samples as well. Bode has used Y-STR testing for mixed DNA profiles from touch evidence obtained from items such as fingernails, clothing, and guns. Bode’s casework analysts have been processing Y-STR cases since the beginning of 2004. In addition to the analysis, our analysts have testified to the results in multiple states.
Bode offers YSTR amplification with the Applied Biosystems platforms using Promega’s Powerplex® Y and Applied Biosystems’ AmpFlSTR® YFiler® PCR amplification kits. Bode has the ability to run the products of PCR amplification on the Applied Biosystems 3100 or 3130xl Genetic Analyzer. Currently, YSTR profiles are analyzed using GeneScan® Analysis Software and Genotyper® Software and GeneMapperID® software.
Y-STRs are paternally inherited therefore all of the individuals in the paternal lineage of a family (i.e. grandfather, father, brother) will share the same Y-STR profile. Y-STR analysis is used in both forensic and non-forensic cases. Y-STR analysis can be used if an individual is missing or unable to provide a biological sample and a living paternal relative is available to provide the necessary DNA sample for comparison purposes. Y-STR analysis can used to exclude an individual, or include an individual from the paternal lineage.