Fossil DNA's potential and limitations
The amount of DNA preserved in the ice cores is small, as it has been incorporated with soil particles for up to several hundreds of thousands of years, where it has been broken down over time. All research is therefore carried out under sterile conditions in dedicated laboratories to avoid contamination from modern DNA material.
Even though the preservation conditions are optimal under the ice in the cold, dry and stable temperatures, there will inevitably be a constant degradation process of the DNA that modifies the base composition of the DNAand destabilizes its helix form. This decomposition results in the DNA manifesting as short fragments of up to a few hundred base pairs and makes it extremely difficult to make more sophisticated statistical analyses of the DNA in the ice.
Current scientific methods do not allow for the study of individual organisms within the ice – organisms that would provide an opportunity to examine population dynamics within species over time. Instead, the conserved fragments are representing groups of organisms, such as bacteria, plants, insects, birds or mammals, propagated so the diversity within the individual groups can be studied.
Modern sequencing technologies make it possible to sequence millions of base pairs within a short period of time and can thus deep sequence an entire sample, which in turn provides insight into the biodiversity of the various organisms or taxonomic groups that lived when the ice was formed.
Developments in DNA sequencing are moving quickly and the prospect ofbeing able to analyse individual molecules in the future paves the way for being able to analyse samples where the DNA content is low.
Ice Core Drilling Projects
For more information on the topic please contact Astrid Schmidt