Ancestry test material (3)

I believe the answer is:

dna

(Other definitions for dna that I've seen before include "Substance in chromosomes that stores genetic information, used by police" , "Genetic material often used by police" , "Substance that stores genetic information - often used by police" , "Genetic-code molecule" , "Genetic code" .)

I've seen this clue in the LA Times.

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