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MAMMALIAN DNA IN PCR REAGENTS
Citation:
SHANKS, O. C., L. HODGES, AND W. REAM. MAMMALIAN DNA IN PCR REAGENTS. Presented at Chacmool International Archaeology Conferenc 2005, Tools of the Trade: Methods, Techniques and Innovative Approaches to Archaeology, University of Calgary, Calgary, AB, CANADA, November 10 - 13, 2005.
Impact/Purpose:
To inform the public.
Description:
Ancient DNA analysis is becoming widespread. These studies use polymerase chain reaction (PCR) to amplify minute quantities of heavily damaged template. Unusual steps are taken to achieve the sensitivity necessary to detect ancient DNA, including high- cycle PCR amplification targeting short (<300 bp), high-copy templates. Often, primers are used that anneal to target sequences from multiple species. These factors increase the likelihood that PCR will amplify traces of highly fragmented DNA, including ancient DNA and extraneous DNA that may contaminate PCR reagents. During our ancient DNA studies, we detected extraneous DNA in 2.1% (17 of 787) of no-template controls. We identified cow, pig, chicken, and human DNA in commercially prepared PCR reagents. Deoxynucleoside triphosphates (dNTPs) are the most likely source. Deoxynucleoside monophosphates are obtained by hydrolysis of animal DNA and then phosphorylated chemically to produce triphosphates. Incomplete hydrolysis of animal DNA during dNTP production is an obvious source of contamination.