The rapid advancement of next-generation sequencing technology, also known as massively parallel sequencing (MPS), has revolutionized many areas of applied research. One such area, the analysis of mitochondrial DNA (mtDNA) in forensic applications, has traditionally used another method—Sanger sequencing followed by capillary electrophoresis (CE).
Although MPS can provide a wealth of information, its initial adoption in forensic workflows continues to be slow. However, the barriers to adoption of the technology have been lowered in recent years, as exemplified by the number of abstracts discussing the use of MPS presented at the 29th International Symposium for Human Identification (ISHI 29), held in September 2018. Compared to Sanger sequencing, MPS can provide more data on minute variations in the human genome, particularly for the analysis of mtDNA and single-nucleotide polymorphisms (SNPs). It is especially powerful for analyzing mixture samples or those where the DNA is highly degraded, such as in human remains. Continue reading
Next week, forensic analysts from all over the world will gather in Minneapolis for the 27th International Symposium on Human Identification (ISHI). So today, we’d like to share one story from a forensics lab that highlights the importance of collaboration, knowledge-sharing and technology development–since that is what ISHI is all about.
Crimes against children are especially heinous, and it is vitally important that the offenders are removed from the streets as soon as possible. In today’s blog, Sarah Chenoweth from the Anne Arundel County Crime Lab in Maryland describes a sexual assault case that was solved in just five days. Key to this speed were the collaboration between lab staff and state police, and the ability to quickly and reliably amplify DNA profiles from low-DNA samples. Thanks to the efforts of the investigators involved, parents in Maryland, and possibly nationwide, can sleep a little easier.
On Friday, February 5th, the Anne Arundel County Crime Lab was notified of a sex offense involving a 7-year-old victim. With our efficient DNA workflow, including use of the Fusion amplification kit with our 3500 Genetic Analyzer, we were able to identify the perpetrator in only five days. Continue reading
Mitochondrial DNA has important implications for forensic analysis. Image Credit: National Institutes of Heath, USA
The 27th annual International Symposium on Human Identification—ISHI 27—will be held September 26-29 in Minneapolis, MN. One of the largest conventions focused on forensic DNA analysis, ISHI features presentations on the latest advances, interesting cases and key issues relevant to the field. In anticipation of this years’ conference, here is a preview of one talk, provided by Dr. Mitchell Holland of Penn State University (Dr. Holland will also be participating in the June 28 TechTour in New York). The focus of Dr. Holland’s research is mitochondrial DNA (mtDNA) analysis and its application to human identification. At ISHI, he will be presenting his recent work using NextGen sequencing to analyze mtDNA heteroplasmy.
mtDNA heteroplasmy was key to the identification of the remains of Tsar Nicholas II
Heteroplasmy is the presence of more than one mitochondrial genome within an individual. Perhaps the most famous example of the effect of mtDNA heteroplasmy on a forensic investigation is the identification of the remains of Tsar Nicholas II. mtDNA from bones discovered in a mass grave in 1991, was identical in sequence to known relatives of the Tsar except at one position, where there was a mixture of matching (T) and mismatching (C) bases. Lingering doubt caused by this result meant that confirmation of the authenticity of the remains was delayed. Ultimately mtDNA analysis provided the needed evidence for identification, showing that the same heteroplasmy was present in mtDNA extracted from bones of the Tsar’s brother, confirming the Tsar’s identity (Ivanov et al., (1996) Nature Genetics 12(4), 417-20).
Here is what Dr. Holland had to say about the work he will present at ISHI: Continue reading
I will admit that over the years, I have watched various crime scene investigation shows and read several books by Kathy Reichs and Patricia Cornwell because I was fascinated by forensic science. These same books and shows are a guilty pleasure because as a scientist, I know these portrayals do not accurately reflect how laboratory work is done. Answers are not so cut and dried as an exact estimation of time of death—for example, death was five hours before the body was found in an abandoned warehouse. However, scientists are always looking for ways to improve accuracy in time of death estimates, which are currently based on a few physical clues that are affected by environment and other factors. One approach taken by Sampaio-Silva et al
. (1) was to assess the RNA degradation using reverse transcription quantitative PCR (RT-qPCR).
The authors of this PLOS ONE article wanted to determine if nucleic acid degradation could be used as a method to improve time of death estimates. Continue reading