Sampling DNA from ancient bones is an elaborate and time consuming process. Ancient DNA is by definition degraded and due to this special precautions have to be taken. After an animal dies the DNA in its cells quickly starts to degrade and continues to do so over time, leading to loss and fragmentation of DNA. In some bones the DNA is even lost completely. This makes ancient samples prone to contamination from modern DNA and much harder get data from compared to modern samples. Luckily, DNA preserves well in cold environments which makes snow patch finds ideal for studying genetic changes far back in time.
Even so, care has to be taken to avoid contamination and further destruction of the DNA in the bones. That means no snacking on dried reindeer meat while handling old reindeer bones! After they are collected from the snow patches, the finds are slowly dried and then stored in a cooler while they await sampling.
After drilling, the samples are ready for a few days of laboratory work with several rounds of chemical treatments including DNA extraction, PCR and eventually sequencing. The end result is hopefully a nice and clean sequence of nucleotides that provides lots of data,
but with ancient samples some days are better than others…
Due to the excellent conditions for preservation in snow patches, the former is luckily usually the case.
For genetic studies on ancient snow patch finds see: