Software checks for high rates of C-to-T transitions at the ends of DNA fragments. If these "nicks" are present, it’s a signature of authenticity.
The study of —genetic material recovered from biological specimens that have not been preserved specifically for genetic analysis—has revolutionized our understanding of evolution, migration, and disease. However, because DNA begins to degrade immediately after death, specialized methods and protocols are required to extract and sequence these "molecular fossils." 1. The Challenges of Ancient DNA Ancient DNA: Methods and Protocols
If the sample has low endogenous DNA (e.g., 99% of the DNA is from soil bacteria), researchers use "baits"—RNA probes that match the target genome—to "fish out" the human or animal DNA of interest. 5. Bioinformatic Authentication The final step is proving the DNA is actually ancient. Software checks for high rates of C-to-T transitions
The goal of extraction is to release DNA from the mineral matrix (bone) while removing inhibitors like humic acids. However, because DNA begins to degrade immediately after
All work must be done in a dedicated "Clean Lab" with HEPA filtration, positive air pressure, and UV sterilization. Researchers wear full-body suits to prevent shedding their own DNA onto the samples.
Synthetic DNA "adapters" are attached to the ends of the fragments, allowing them to bind to the sequencing platform.
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