Isolation of DNA from small amounts of elephant ivory

Abstract

This protocol describes a method for the extraction of DNA from elephant ivory. These techniques are being used to assign geographic origin to poached ivory by comparing the ivory genotype to a geographic-based gene frequency map, developed separately. The method has three components: ivory pulverization, decalcification and DNA extraction. Pulverization occurs in a freezer mill while the sample is deep frozen in liquid nitrogen, preventing degradation of DNA during the process. Decalcification involves repeated agitation of the sample in 0.5 M ethylenediaminetetraacetic acid over a 4-d period. Extraction follows a modified Qiagen protocol for the extraction of DNA from animal tissue. This method can be used on all forms of ivory. However, DNA recovery is highest when the outermost layer of the tusk, the cementum, is used. When applied to extract DNA from 11 samples, in duplicate, the entire protocol can be completed in 6 d, although much of this time consists of pause points that do not require effort. The protocol provides 0.8 ± 0.11 ng μl⁻¹ (mean ± s.e., n = 48) of DNA per sample.