Dimitris Kafetzopoulos, molecular biologist, research director at the Institute of Molecular Biology and Biotechnology in Crete as the first in Greece with special ancient DNA analysis laboratory from mid-January 2015 explains the conditions to TheTOC.gr
“The steps are as follows: The immediate harvesting of tissue preferably from molars, which should have been frozen in order not to be touched by human hands since its discovery. Archaeologists count bones, wash and weigh them. This does very much damage in the case of DNA analysis, in the sense that anyone who touches them leaves his own DNA. So the first step is the timely collection by scientists who will do the analysis. This could be facilitated so that stored tissues and we can come to some understanding about the analysis. ”
“The analysis should be done by, at least, two independent laboratories. This is a common practice, which ensures the result. Only when two-or three, even four, depending on the available resources (money), but also on the amount of skeletal material, agree on the findings, we can be sure. ”
If the tomb was sealed -which it was not- there is a good chance that the skeleton would have been left as dry as possible. However, because the area was flooded (as seen from the debris, soil, and other materials of the fill), the probability of the DNA being rinsed, even the hidden areas of the teeth, is great.”
“It will be worth checking the DNA of all of the excavation team. Here there is a difference: There are laboratories that do DNA analysis and there are workshops that do ancient DNA analysis. Most likely the analysis will show that the … skeleton of Amphipolis is that of Ms Peristeri or an associate. They would never say that, I suppose, but consider what would happen if there were inattentive and had not used gloves or had not taken additional measures. I know they were cautious. ”
“The skeleton must remain under control of the scientific officer of the excavation and not be shared left and right. We are talking about taking a sample. Depending on the amount and condition of the tissue, a consultation will ensue on the manner according to which the distribution of skeletal material will take place.
The molecular biologist who will take the sample using special mills which crush the tissue (bone) at very low temperatures to ensure that there is no alteration, heating etc. The method is used when we have at our disposal very hard tissues (bones, seeds, etc.), in tightly closed tubes as to avoid their contamination from the environment.
The sources of infection are dependent on the case. If you are interested in human tissue – a skeleton, the main danger is us. If you are interested in plant tissue, the risk is any plant beside it, pollen that circulates, etc.
If the sample is infected with something alien, at the end of the analysis we will be able to pick out foreign material, but in human material this is very difficult, simply because it is difficult to say if it’s my own DNA or that of the deceased.”
“Sex and age can be found by anthropometrists and anthropologists from the skeleton. If there is a skull or pelvis and they are in good condition, then one can discern sex almost immediately.
Age is also something that can be determined from the bone condition. The bones degenerate when we get older, there are lesions, osteoporosis and it shows. With a relative deviation, age results can be found directly.”
Also, a partial burning of the dead, usually helps DNA being maintained because it is ‘trapped’ in the bones and there is no oxygen. If complete combustion took place, incineration, there is no possibility to find something. That is, in residues from fires that we find in caves, for example, bones of animals used for food and not cremated, but baked, cooked, enable us to find remnants of ancient DNA.
For the dead of Amphipolis I do not know what has happened, data speak of a simple burial.”
What happens in case of Amphipolis, where the tomb is full of sand flooded from lake Kerkinitis and the river Strymon? TheTOC.gr asked Mr Kafetzopoulos.
“If it was a sealed tomb -which it was not- there would have been a good chance for the skeleton to have been left as dry as possible. However, because the area was flooded(as seen from the debris, soils, and other materials of the fill), theprobability that the DNA has been rinsed, even the hidden areas of the teeth, is great.
So be careful. Do not be disappointed if the DNA that we get is only that of the research team. This will happen for sure.”
“As the surgeon before entering the operating room has declared what he will do and writes down a protocol, I too will follow a similar procedure, I myself, follow current practices, I have a sample handling protocol. After tabling the protocol and having the tissue, I make a “library” of the sample -the material, the dust I have received- which I put into a machine to scan the fragments. Finally, at best we can read pieces from 25 bases. ”
“Human DNA is composed of lengthy chunks that contain a few hundred million bases. The letters of DNA are sentences in which our genetic code is written. We usually read, small areas. An ancient DNA has fallen from a few hundred million bases to just 25 ‘letters’. Therefore, you must read this little ‘book’ word for word.”
“A sample analysis takes about 10-15 days. After that, begins his study. If there is available tissue, it is advisable to take a sample from another area of the skeletal material. That is, to obtain a sample from a molar and the acetabulum, which is also a sufficiently sheltered position. After that, we analyze whichever is better.”