Success begins with choosing the right material. The (part of the skull) and tooth cementum are the "gold standards" because their high density protects DNA from environmental leaching.
Modern DNA from researchers or the environment is "fresher" and more intact than aDNA, making it easy for a tiny amount of modern DNA to overwhelm the ancient sample. 2. Sample Selection and Preparation
Working with aDNA is fundamentally different from modern genomics due to three primary hurdles:
Over time, DNA strands break into very short fragments, typically between 30 and 100 base pairs.
Deamination (the conversion of cytosine to uracil) occurs frequently at the ends of fragments, leading to sequencing errors (C-to-T transitions).
Samples are ground into a fine powder and soaked in EDTA, which chelates calcium and dissolves the bone matrix.
