Can Forensic Quality DNA be Extracted from Discarded Gum?
Channel: AZ Bio
Date: 2020-09-13

Can Forensic Quality DNA be Extracted from Discarded Gum?

Presented by Yakeleen Almazan and Asher Bankhead, Pueblo High School

The purpose of our research is to determine whether forensic scientists can accurately use gum samples to extract Deoxyribonucleic Acid (DNA) and identify suspects. This research is especially helpful for forensic scientists who extract DNA to solve cases. 

Evidence is a scarce resource for forensic scientists. We wish to determine if a mundane source like chewing gum can yield stable forensic quality DNA, and at what time frame. Furthermore, this involves the stability of the mitochondrial Cytochrome B gene over time.

DNA from the chewing gum was isolated and specific primers were used to amplify a part of Cytochrome B gene. Electrophoresis was performed with a gene ruler that allowed us to measure the gene product (measured by base pairs) and see if we isolated the correct gene. Other samples were sequenced and compared to the isolated part of the Cytochrome B gene. 

The first set of results we got were our electrophoresis gels. There were two qualifiers that made the data forensic quality. The first qualifier being the amount of base pairs in our product. Nearly every sample was close to 230 base pairs. The other qualifier was the amount of DNA, which was determined by the brightness of the electrophoresis bands (products) which were variable. To judge them based on brightness, we created a scale from 1-5 based on the luminosity. The amount of DNA over time didn’t decrease by any meaningful amount. After visual analysis, we also received DNA sequencing on our gum samples. The sequencing found a 99% similarity to the part of the Cytochrome B gene we isolated. With the amount of DNA in the electrophoresis not decreasing, and our isolated genes being nearly identical, it is likely that gum found in DNA doesn’t decrease in quality up to a year, making it useful for forensic scientists.

Although we were focused on the mitochondrial DNA of the gum sample, it is unethical to use such analysis in a classroom because our work could potentially point us to an individual who has not committed a crime. Therefore, we used the cytochrome B gene in the mitochondrial DNA because its sequence is highly conserved and stable among humans. If we were to do forensic analysis on our gum samples, we would look at the variable region of the Mitochondrial DNA which would connect us to Haplogroups and eventually, a suspect. In the future we hope to conduct this experiment in various environments to examine how these variables impact the DNA stability.