Since the discovery of techniques that allow for DNA analysis and sequencing, not only did it impact the field of genomics, but it also stimulated other fields of applications. (Capelli et al, 2003). Two unconventional and ways of applying these techniques, ancient DNA (aDNA) analysis and forensic DNA profiling (Capelli et al, 2003), are branches of this discovery that intertwine in respect to their methodologies and approaches.
In this commentary, I will attempt to analyze the criteria of authentication, the different aspects of the purpose of DNA analysis, and the problems regarding contamination of the two unconventional applications of DNA analysis. DNA analysis has become an effective procedure in forensic genetics. Prior to 1985, the methods of analyzing biological samples were limited to only conventional blood group and enzyme analysis in criminal cases (Capelli et al, 2003). These methods were informing but nevertheless only gave surface analysis.
The advent of the polymerase chain reaction (PCR) changed this phenomena and made DNA analysis an endless scope applicability. Capelli et al states that it allowed forensic experts to address the most inaccessible sources of DNA evidences (such as cigarette butts, fingerprints etc. which are predominant in criminal cases) On the side of ancient DNA analysis, it provided opportunities for scientists to ‘go back in time’ and study the genetic relationships of extinct organisms to their contemporary relatives. (Holfeiter et al, 2001).
On the other side of this tantalizing advent of DNA analysis, there are many problems regarding the verifications of the results of analysis. Severe fragmentation of the DNA molecule can occur in some forensic specimens, making them look like ancient genomes (Capelli et al, 2003). Cooper and Wayne (1998) addresses in his article that the unifying component is that preserved DNA is damaged over time by processes such as oxidation and hydrolysis, leaving only traced amounts of DNA fragments containing cross-links and modified bases.
This causes a problem for both aDNA and forensic scientists, they are responsible for the low recovery rate of undamaged DNA from archaeological specimens (Kalmar et al, 2000). Capelli et al (2003) further mentions a number of experimental asperities in the two fields. One is that nucleotide base pairs are often degraded down to 100-300 bp or less. When degraded nucleotides initiate a reaction, many repetitions become necessary and verification is needed to validate that nucleotide misincorporations do not influence the result (Holfeiter et al, 2001).
Other experimental asperities include critically low amounts of molecule per gram of specimen. PCR inhibitors also cause a problem. In Kalmer’s article of PCR amplification, he reports that the inhibitors could prevent the successful amplification of mitochondrial DNA fragments. This is also important in forensic DNA analysis. Overall, these problems are commonpoints between the two fields of study. The last controversial topic I would like to discuss is the authenticity of results.
In the past many purportly sound publications of ancient DNA have turned out to be unauthentic. Great precautions need to be taken in order for the results to be considered authentic. This issue has been increasingly important in both fields of study. Modern human DNA is one of the biggest sources of contamination at many stages of the experiment, hence, the extraction and preparation of the PCR must be done in the laboratory that is rigorously separated from work involving modern DNA (Holfeiter et al, 2001).
The basic outfit of an aDNA workstation includes extensive employment of disposable labware and coats, filtered tips, facial masks and UV lamps to irradiate the workbench. Also, many measures of internal control are introduced at every step of the procedure in order to minimize any contamination. These include extraction and PCR blanks (which are controls) (Capelli et al, 2003). When taken as a whole, all these precautionary measures in order to fulfill the criteria of authenticity are conventional procedures practiced both with aDNA analysts and forensic scientists.
In the past few decades there has been a spectacular uprise in DNA analysis, especially of its tantalizing application in two unconventional areas of study of ancient DNA analysis and forensic science. There is no doubt that the methodologies and approaches of the two are intermingled and are common in many aspects including technical measures regarding authenticity and contamination. The future holds virtually unlimited room for new discoveries and methodologies that would benefit the two disciplines.
Capelli, C. , Tschentscher, F. , Pascali, V.L. 2003. “Ancient” protocols for the crime scene? Similarities and differences between forensic genetics and ancient DNA analysis. Forensic Science International 131:59-64. Cooper, A. , Wayne, R. 1998. New uses for old DNA. Current opinions in biotechnology 9:49-53 Holfreiter, M. , Serre, D. , Poinar, H. N. , Kuch, M. , Paabo, S. 2001. Ancient DNA. Nature Reviews 2:353-359. Kalmar, T. , Bachrati, C. Z. , Marcsik, A. , Rasko, I. 2000. A simple and efficient method for PCR amplifiable DNA extraction from ancient bones. Nucleic Acids Research 28(12):e67i-e67iv.