Investigation of STR sites from DNA samples extracted from human teeth exposed to increased doses of gamma radiation

Background and Aim: Short tandem repeats are the most important genetic markers in identification tests because of their high discrimination power. Many mechanisms have been studied that cause damage to DNA resulting from many genetically toxic substances such as ionizing radiation (alpha - beta - gamma), which may affect the STR sites and thus on identification purposes, especially in places that have been exposed to explosions and the use of radioactive materials. The study aims to study the effect of gamma radiation on the stability of STR sites of DNA samples extracted from human teeth (molars) exposed to increased radiation doses 0- 250-350-450 kGy in order to investigate their importance as legitimate samples in identification under these conditions.

Materials and methods: healthy dental samples were taken from people who extracted their molars for an unsatisfactory reason (such as orthodontic purposes) in order to preserve the pulp of the tooth that contains the largest amount of DNA. DNA was extracted using a DNA isolation kit from the tooth of Qiagen, followed by amplification of the samples by polymerase chain reaction (PCR) using a kit from the same company, followed by capillary electrophoresis, Using analytical software to read the results of the migration of  each str peak, the results were then analyzed.

Results: At the radiation dose of 250 kGy, we did not observe the disappearance of any of the STR sites studied on the capillary electrophoresis profile as compared with the control not subjected to radiation, although their peaks decreased due to the degradation of some DNA molecules by the effect of ionizing radiation, and starting from the radiation dose of 350 kGy, it was not possible to amplify the large molecular weight genetic sites (D2S1338-D21S11-Vwa-D19S433 D2S1338-FGA-D8S1179) in some samples as a result of their degradation by ionizing radiation.

Conclusions: Teeth are important forensic samples that can be used as a sample for identification purposes when it is not possible to identify the victims of war and disasters using other sample sources ,because of their ability to preserve DNA from the influence of surrounding factors for periods longer than other sample sources.