Effects of Temperature and Time since Deposition on Recovery of DNA from Touch Samples

DNA can now be recovered from the residue left behind on touching an object. The source of this DNA is relatively unknown, therefore there is little knowledge about its dependence on environmental factors, if there is any. Since forensic DNA analyses often involves dealing with trace amounts of samples, how these samples are stored and how they are affected over time is a critical issue. This thesis focuses on extracting DNA from “true fingerprint” i.e. touched samples and from “mock fingerprint” i.e. in which a known quantity of DNA is deposited as a fingerprint. Real-time PCR was carried out on the samples to quantitate the amount of DNA recovered after the samples were exposed to different temperatures and time points. Agarose gels were run and stained with 1X SYBR Gold to visualize any degradation in DNA recovered from true fingerprints due to temperature and time since deposition. Statistical analysis conducted using ANOVA revealed that temperature affected DNA recovery only after 3 weeks of storage and even at 4°C, amount of DNA recovered from samples significantly declined after 1 month. The use of “mock fingerprints” led to generation of standard curves and the degradation pattern of samples was studied, validating future use of “mock fingerprints” in touch DNA research.