Reports

Amino Acid Racemization and the Preservation of Ancient DNA

Science  10 May 1996:
Vol. 272, Issue 5263, pp. 864-866
DOI: 10.1126/science.272.5263.864

Abstract

The extent of racemization of aspartic acid, alanine, and leucine provides criteria for assessing whether ancient tissue samples contain endogenous DNA. In samples in which the D/L ratio of aspartic acid exceeds 0.08, ancient DNA sequences could not be retrieved. Paleontological finds from which DNA sequences purportedly millions of years old have been reported show extensive racemization, and the amino acids present are mainly contaminates. An exception is the amino acids in some insects preserved in amber.

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