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Forensic DNA analysis of the Arbeia skeletons

Forensic DNA analysis of the Arbeia skeletons by Dr Eleanor Graham of Northumbria University.
My name’s Eleanor Graham. I’m a senior lecturer in forensic science at Northumbria University, and I’m going to be talking to you about some DNA work that we’re doing on the South Shields skeletons found in the courtyard house at Arbeia. These two skeletons are of particular interest because they both show evidence of a traumatic death and decomposition before burial. This is a very unusual finding in this context, so that’s why we’re going to try and find out a bit more about them. So what we’re going to do - is we’re going to attempt to extract any remaining DNA from two teeth samples that we’ve collected from the skulls of these individuals. These samples present unique challenges.
The two biggest challenges that we face are the age of the sample, which means that the DNA can be in very poor, what we call degraded condition, meaning that some of the markers that we’re interested in may no longer exist. The other big challenge that we face is contamination with modern DNA, and also environmental samples, which may contaminate our sample and prevent the analysis work that we’d like to do. In forensic science, we try and use tests in the laboratory to answer a particular questions. In this case, the questions that we would like to answer are, are these skeletons male? Where did they come from? And what did they look like?
We will be attempting to amplify up regions of DNA to help us answer these questions. In order to recover the DNA from a tooth sample, we first need to clean the exterior surface at this tooth. We need to remove any traces of soil or other dirt that may be sticking to the surface, and we also need to remove any modern DNA, which may have been placed there by people handling this sample since it’s been excavated. We do this by washing the tooth using DNA free water and a weak bleach solution. Once we’ve washed the tooth, we will then UV treat it, so that any contaminating DNA left on the surface is damaged so that we cannot examine it.
In order to recover the maximum amount of DNA from the tooth sample, what we need to do is to crush it down into fine powder. This allows our DNA extraction chemicals to access the material bound within the tooth matrix. The first thing we do is to cut the tooth into smaller pieces using a handheld drill.
Once the tooth’s in smaller pieces, we can then load it into our freezer mill apparatus. This freezer mill contains liquid nitrogen, which cools the sample down. Once the sample has cooled, we then use a metal slug under a magnetic field, which moves backwards and forwards very quickly crushing the tooth down into a very fine powder.
Once the tooth sample has been powdered, we can then move onto the DNA extraction process. This process involves the removal of every components other than the DNA itself. The first thing we need to do is to digest down the power and the minerals and remove everything else from the solution. In order to do this, we first use a lysis buffer, which will digest all the remaining tissue. We leave this to incubate over night. Once the incubation is complete, we can use a silicate suspension to recover the DNA from the solution that remains. So once we’ve recovered our purified DNA, we can move on to the analysis phase of the investigation.
The first thing that we’re going to do is to perform some quality and quantity tests. The tests that we perform now will give us some information about how much human DNA has been recovered from the tooth, and what condition it’s in. This kit, additionally, will tell us something about the biological sex of the individuals. Once we have this information, we are hoping to send the sample off for some further testing using a next generation DNA sequencing technique. This technique analyses a number of markers, which can tell us a lot more about this individual, including where in the world they might have come from, and what they may have looked like.
We’re hoping that these results will give the archaeologist some answers to the questions that they have.
Following the very first run of Hadrian’s Wall in 2014 we joined up with Dr Eleanor Graham from Northumbria Centre for Forensic Science and Dr Nick Hodgson and Alex Croom from Tyne and Wear Archaeology to undertake DNA analysis of the South Shields skulls found in the courtyard house at Arbeia.
In this video Dr Eleanor Graham shows us some of the steps involved in DNA analysis. If archaeological reality were anything like the fantasy world of TV’s CSI we would have had some splendidly uncomplicated results back by now – but of course it is not.
Our first results have revealed two very important bits of information. First, they have confirmed that we can potentially get excellent DNA information from the teeth. This is in itself important; contamination can derive from a multiplicity of causes. The second is that we can confirm the biological sex of the two individuals, both were male. But for further data we have to wait.
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Hadrian's Wall: Life on the Roman Frontier

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