MBE Advance Access published online on January 25, 2007
Molecular Biology and Evolution, doi:10.1093/molbev/msm015
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Research Article |
More on contamination: The use of asymmetric molecular behaviour to identify authentic ancient human DNA
1 Evolutionary Biology, Uppsala University, 752 36 Uppsala, Sweden
2 Centre for Ancient Genetics, Niels Bohr Institute and Biological Institute, University of Copenhagen, Denmark
3 The National Board of Forensic Medicine, Department of Forensic Genetics and Forensic Toxicology, Linköping, Sweden
* anders.gotherstrom{at}ebc.uu.se, Phone: +46 18 4716483, Fax: +46 18 4716310
Accepted for publication January 22, 2007.
Authentication of ancient human DNA results is an exceedingly difficult challenge, due the presence of modern contaminant DNA sequences. Nevertheless, the field of ancient human genetics generates huge scientific and public interest, thus researchers are rarely discouraged by problems concerning the authenticity of such data. Although several methods have been developed to the purpose of authenticating aDNA results, while they are useful in faunal research, most of the methods have proven complicated to apply to ancient human DNA. Here we investigate in detail the reliability of one of the proposed criteria, that of appropriate molecular behaviour. Using real-time PCR, and pyrosequencing, we have quantified the relative levels of authentic ancient DNA, and contaminant human DNA sequences recovered from archaeological dog and cattle remains. In doing so we also produce data that describes the efficiency of bleach incubation of bone powder, and its relative detrimental effects on contaminant and authentic ancient DNA. We note that bleach treatment is significantly more detrimental to contaminant than to authentic ancient DNA in the bleached bone powder. Furthermore, we find that there is a substantial increase in the relative proportions of authentic DNA to contaminant DNA as the PCR target fragment size is decreased. We therefore conclude that the degradation pattern in ancient DNA provides a quantifiable difference between authentic ancient DNA and modern contamination. This asymmetrical behaviour of authentic and contaminant DNA can be used to identify authentic haplotypes in human ancient DNA studies.
Key Words: contamination • ancient DNA • authentication