Challenges and Issues in DNA extracted from formalin fixed and paraffin embedded human tissues for forensic investigations

Abstract

Preservation of human tissues in fixatives is an important constituent of medical diagnostic procedures and clinical research employed to prevent the autolysis, putrefaction and degradation of the tissue and tissue components. Utility of such materials is important for forensic investigations where archived pathology specimens represent the only reference source of DNA available for positive identification, vast majority of which have been preserved in formalin. Apart from the excellence of this fixative for maintaining tissue integrity, it has no doubt a profound effect on extracting DNA from the tissues because of time dependent degradation, extensive covalent protein-protein network and protein-nucleic acid cross-link network generated by buffered formalin which heavily challenge DNA recovery for downstream PCR- based STR typing applications for forensic related issues. Since the success of comparative genetic analyses lies in the acquisition of comparable quality and quantity of DNA extracts, it is important to stress on contamination free working environment along with optimization of the extraction procedure in order to recover the highest percent of DNA from the sample without introducing any chemicals or reagents that may interfere with subsequent downstream analysis