Young Investigator Mirna Ghemrawi on identifying unknown non-human DNA samples
Mirna talks about creating an easy assay for species identification in criminal cases
May 11, 2020
The new Investigator blog shines a personal spotlight on individual scientists at the exciting early stages of a career working in the field of human identification and forensics. The passion and commitment revealed in their stories are an inspiration to all in our community.
This month we go behind the scenes with Mirna Ghemrawi, a doctoral student at Florida International University. Mirna has traveled a long distance from Lebanon to FIU where she is working on species identification with a particular focus on Pyrosequencing-based DNA analysis.
Tell us about your background and how you became interested in forensic science?
Ever since I was young, because I had lighter skin than my siblings, they always teased that I was not part of the family and that I mistakenly had been switched in the hospital. Thus, I always wanted to dig into my Family’s DNA to prove them wrong, not knowing that it was all a joke. I was also very intrigued by Crime Scene Investigation shows, from animation ones to documentaries, and decided then that I wanted to be a forensic scientist. Despite those shows being mostly fictional, they have some elements of reality.
Forensics was not well-established as a major in Lebanon. However, after I finished my undergraduate studies in Medical Laboratory Sciences, I was granted a Fulbright Scholarship to pursue my Master’s studies in Forensic Science in the United States. I was lucky to have hands-on experience from sample collection to data analysis in Forensic DNA phenotyping, predicting eye, hair and skin color of a Lebanese admixed population.
The more I learn about DNA and its power in solving crime cases, the more I want to study and participate in research about it. My passion towards forensics led me to start my doctoral studies at FIU where I am mainly interested in microbiome and species identification for forensic applications.
Can you provide a summary of the project you are working on?
The project that I am working on is a collaboration with Dr Bruce McCord’s lab and QIAGEN to create an assay for species identification. On many occasions, biological samples found in crime scenes are not human in origin, but could be biological stains from pets, livestock meat, or mixtures. With the advancement of sequencing technologies, such as Pyrosequencing, we were able to develop a quick and easy method to identify miscellaneous samples by targeting a small gene in the mitochondria genome. This assay has been shown to be a robust and sensitive one that can generate full profiles from minute and degraded samples such as bone, teeth, hair, saliva and blood.
Please describe your typical day in the lab.
A typical day in the lab usually starts with a good cup of coffee (outside the lab for safety purposes). I would then go through my to-do list for the different sets of experiments, data analysis, seminars, teaching and grading, so I can prioritize what comes first. I then try to start conducting experiments first and fill in the incubation/waiting times with other tasks. I am still learning how to be more organized in documenting my notes (colored pens and papers are still my favorite routine). In general, I enjoy being in the lab especially that we have a nice environment where I can share thoughts and ideas with my lab-mates on our projects. Being a member of a team is very important. If it is a good day, I would get good results, but some other days, it is mostly a trial and error process.
What do you find most interesting about your project? Have you seen any surprising results?
I really enjoyed working on this project all the way from getting the approval from the ethics committee to actually presenting my work in two big forensic conferences. I had unique sets of samples like chimpanzees, monkeys and lemur stains that are at least 18 years old. I did not expect to get them to amplify, but they worked just fine. I also enjoyed extracting DNA from bones and hairs. One surprising result was finding out a one-base difference between a warthog (wild pig) and domestic pig (pork meat) in the small target we are sequencing.
What are the benefits of your project?
This assay is an easy, robust and relatively cheap method to identify miscellaneous non-human samples. It will provide forensic DNA analysts with an investigative tool/kit that is deemed essential in helping solve criminal or poaching cases. It doesn’t require complicated hands-on-time or bioinformatic knowledge. The PyroMark software used for the QIAGEN Pyrosequencer, is user-friendly and is used to create the input file and to generate a report (that is the sequence of the DNA sample). This sequence can then be searched as a query against a curated database of known species. With the PyroMark Q48 Autoprep instrument, 48 different samples can be sequenced simultaneously in no more than 180 minutes. So, I think it will be a valuable kit in the forensic market for implementation in criminal casework.
What are the major challenges faced while working on your project and how do you overcome them?
One of the main challenges was the mixture analysis. Different primers have been designed and tested to overcome preferential amplification of one species over the other. Another challenge was differentiating closely related species. While this assay can differentiate a dog v. a cat for example, it cannot resolve sub-species differences. Nonetheless, in a forensic casework, what would be more critical is to identify the non-human sample on the species level. Further analysis using more targets can be employed for deeper differentiation.
Which QIAGEN products do you use and what do you like about the products?
I use many QIAGEN products from DNA extraction, to PCR amplification to sequencing kits. What I like about QIAGEN products and instruments is the ease of use. What I also appreciate is the customer service provided by QIAGEN. A team of experts in different disciplines all work together to give the best service.
My favorite workhorse is the EZ1 Advanced, an automatic extraction instrument based on silica-coated magnetic beads chemistry. I put in the cartridge, then the samples and hit the start button, and 16 minutes later, it is DONE, it is an EaZy ONE.
Outside of forensic science, what are your hobbies?
Well, I love everything about table tennis. I try my best to find time to smash some balls. I sometimes feel bad for my roommates when I start to hit the ball on the paddle and the walls. I also enjoy biking when it is a good Miami day which is often.