TITLE: Forensic DNA Typing in a Population
AUTHOR: Robert Jack
SCHOOL: Hamilton-Wenham Regional High School
SCHOOL ADDRESS: 775 Bay Road
In forensic investigations, a crime scene sample of DNA must be matched to a suspect’s DNA. Since it is impossible to test the entirety of both samples, specific loci are tested and then compared to a population for identification. The purpose of my experiment was to analyze the VNTR locus DIS80 in the population of Hamilton-Wenham Regional High School.
To do this, I collected saliva samples from 38 unrelated individuals at my high school. I then extracted the DNA from the epithelial cells and amplified each sample using the polymerase chain reaction (PCR). The samples were then analyzed by agarose gel electrophoresis, and photographed under UV illumination. Using the known molecular weights of standard markers, I determined the molecular weight of each gel band. Leach allele was assigned a allele number, based on the repeat units of DIS80. Finally, the data was analyzed to project its representation of the entire school population.
The accuracy of the samples was within 10 base pairs. This was determined using samples that had been amplified multiple times and analyzed separately. Therefore, a total of 15 separate genotypes were identified among the sampled population. Alleles 6 and 11 were observed to have the highest frequency. These high frequencies correlate to the distribution of a previous genotyping experiment with a Caucasian population. I applied the Hardy-Weinberg Law to the allele frequency data, and then determined the variation from an ideal equilibrium. Lastly, by using a 95% confidence interval, I calculated how the sample allele frequencies might compare to the allele frequencies in the entire school population.