1Biotechnology Department, College of Biotechnology, University of Modern Sciences, Dubai, UAE
2Forensic Medicine and Clinical Toxicology Department, Faculty of Medicine, Alexandria University – Egypt
3Forensic Medicine and Clinical Toxicology Department, Faculty of Medicine, Mansoura University, Egypt
4Forensic Medicine Department, International Medical School (IMS), Management and Science University (MSU), Malaysia
5Forensic Medicine and Clinical Toxicology Department, Faculty of Medicine, Cairo University – Egypt
*Corresponding Author: Prof. Sohayla M. Attalla, sohayla@msu.edu.my
Online Published on 22 December, 2021.
Forensic science has flourished extensively within the past two decades and is proven to be the key to resolve criminal investigations. The main problem faced by the forensic scientists is the preservation or stability of the DNA within the biological samples. The present study aimed at investigating the effect of different environmental conditions on DNA degradation in forensic DNA casework. Human blood samples were taken from 8 willing individuals then each sample was divided into 21 fractions. This study was conducted over a period of 3 weeks. The tests were performed at four different temperatures (55° C, 35° C, 25° C and 4° C) and four different humidity ranges (RH) (41%, 55%, 58% and 62%) Corresponding to Dubai weather conditions. DNA extraction has been performed using the Norgen blood DNA isolation – (mini kit), followed by DNA quantification using the Quantifiler ™ human DNA quantification kit.
At temperature of 55°C and at a relative humidity of 41%, the average amount of DNA at day 1 was 40.98 ± 0.67 ng/μl. A gradual DNA degradation occurred from day 2 (40.20 ± 0.51) through day 10 (0.52 ± 0.24 ng/μl). At day 11 the amount of DNA actually decreased to 0 ng/μl indicating complete DNA degradation. A slight gradual but not much significant degradation was observed at temperature of 35°C and an RH of 55%. Amount of DNA decreased only slightly over a period of 21 days showing a negligible degradation at temperature of 25°C and at an RH of 58%. At the temperature of 4°C and relative humidity of 68% quantity of DNA measured at day 21 showed no decrease or no degradation as compared to the amount measured at day 1. In conclusion, the current study has revealed that DNA is susceptible to degradation and damage under dry and hot environmental conditions i.e. high temperature and low humidity (55C, 40%) and (35C, 55%). On the other hand, DNA can be highly preserved or protected from damage in humid and cold environmental conditions i.e. low temperature and high humidity (25C, 58%) and (4C, 68%).
Forensic science, DNA, degradation, humidity and temperature
