Effect of different environmental conditions on quality of DNA extracted from human teeth for gender determination

Abstract

Use of morphological characteristics in human identification maybe difficult in conditions where human remains are grossly fragmented, decomposed and/or mutilated, or when only a tooth is available. The study aims to ascertain and compare the quantity of DNA from teeth exposed to different environmental conditions using organic and silica column DNA extraction methods and determine their gender using amelogenin gene primer. Human teeth were used and divided into four major groups based on different exposure types (buried in soil, storage in Lagoon water, normal environmental condition by placing them on the floor at the botanical garden, and exposure to temperature of 210oC for 15mins). The powdered dentin-cementum complex was used for DNA extraction, quantification and purity assessments. Amplification was done using amelogenin gene primers. Mean DNA concentration and purity were 187.59±26.25ng/μl and 0.97±0.07 respectively for silica column method, and, 138.98±35.71ng/μl and 0.91±0.11 respectively for organic extraction. With organic extraction, the least and highest mean DNA concentration are from teeth immersed in Lagoon water (74.86±61.19ng/μl) and teeth exposed to temperature of 210^oC for 15mins (385.14±106.39ng/μl). In the Silica column method, teeth heated at 210^oC for 15mins showed the lowest mean DNA concentration (165.57±33.82ng/μl) while teeth exposed to "normal environmental conditions", gave the highest DNA concentration (218.46±45.03ng/μl). Positive and negative male identification were 30.8% and 69.2% respectively, while female identification was 100% positive irrespective of the environmental exposure. The dentine-cementum is a valuable DNA source for forensic investigations. Male identification using amelogenin gene, should still be investigated in the Nigerian context.