Question: Studying ancient DNA must be very difficult, especially hair, how much information can you find out from doing this?

It is very challenging! Before I get to answering your question, this is actually a very large area of research and discussion, so I apologise for the long answer!

There are many factors that determine what sort of information we can get from ancient DNA specimens and hair. Usually the DNA is in very bad form – it is really degraded and in very low concentrations, so contamination is a big issue. Furthermore, standard methods don’t work very well, so researchers have had to develop many specialised methods to be able to retrieve and analyse the very fragmented pieces of DNA found in hair and other sources of ancient DNA.

Most ancient DNA research has been focused on mitochondrial DNA (mtDNA). Mitochondria are small organelles in our cells that provide the cell with energy. They have their own circular genome, of which there are thousands of copies of. This is contrast to our cellular (or nuclear) genome, of which there are only two copies. The nuclear genome is what encodes for all of our genes, and is the genetic information we inherit from our parents – one copy from each parent in fact. As DNA degrades, mtDNA has many more copies, so it takes longer to degrade beyond the point of detection and is therefore more likely to be able to be successfully analysed than the nuclear genome. mtDNA is only transferred from our mother, and does not recombine, so it can tell us a lot about a person’s ancestry. Certain mtDNA mutations are linked to certain geographical locations, so mtDNA has been used extensively for tracing human origins and for population genetics, and even for sorting out evolutionary relationships between species. However, our nuclear genome is more informative as it contains all our genes, and contains a lot more mutations. So while there is more mtDNA and it is easier to analyse it might not be as useful as nuclear DNA, especially when it comes to studying extinct species in ancient DNA research or in the case of forensics, being able to identify people through DNA .

It is only in recent years that methods have advanced enough to enable nuclear DNA from ancient specimens to be sequenced. Most of this technology enables large amounts of DNA sequencing to be performed, enabling coverage of even the smallest traces of ancient DNA in an extract. With enough sequencing, eventually nuclear DNA is sequenced. This technology has allowed the sequencing of a Neanderthal genome, a woolly mammoth, and more recently, a new type of human called a Denisovan, which is different from both Humans and Neanderthal.

When it comes to hair, mitochondrial DNA is easy to analyse – there is plenty of it in hair shaft. However you might be surprised to know that whole nuclear genomes have been recovered from hair – the DNA for the woolly mammoth genome was extracted from a hair sample, as has an Australian Aboriginal and a Paleo-eskimo. In all cases however, up to several grams of hair was used (which is a lot of hair!). The DNA was shown to be fragmented but by using cutting edge DNA sequencing technology, the researchers were able to do a lot of sequencing to get enough DNA sequence to piece together a draft genome.

In my research however, I need to be able to try to analyse DNA from single hairs as this is what is usually found at crime scenes. So while there is nuclear DNA in hair, in order to analysis it you generally need lots of starting material – single hairs are just that bit more of a challenge. I’m working on taking the methods used for large amounts of hair and refining them further so they work on single hairs, however I’m still working on my project, so it will be a few more months before I’ll be able to tell you whether I’ve been successful.

Despite the challenges of using degraded DNA for research and in forensic identification, thanks to massive improvements in technology and method development, it has become possible to get lots of genetic information from very degraded, and small specimens!