Genealogy and DNA are key to providing answers to the identity of the Greyfriars skeleton discovered in Leicester in September. Mitochondrial DNA taken from the bones is being matched to the DNA of a modern descendant of Richard III. The process has been a mixture of science and historic detective work. But is it convincing proof?
Greyfriars DNA Analysis
DNA, or deoxyribonucleic acid, transmits genetic information from an individual to their children. Consisting of a unique four letter code, the DNA sequence in the human genome contains all the information needed to create a person. But the more often the sequence is replicated, the more ‘mistakes’, or variance, occur. It is the frequency of these mistakes that determines how closely related people are. The less variance there is in the codes of two people, the more closely related they are.
DNA was extracted from the teeth and long bones of the Greyfriars skeleton by a small team of five geneticists led by Dr. Turi King of Leicester University. “I am doing all the modern work,” said Dr. King in an interview with Decoded Science. “In one lab I’ll be doing the aDNA (ancient DNA) work with guidance and in the other lab I’m taking the sample and staying while someone processes it independently. In total there will be five people and, if I need to do further sequencing, then one other person involved.”
DNA is easily contaminated, and even breathing is hazardous to a sample. Dr. King and the excavation team took precautions against this. “Both Jo [Dr. Jo Appleby] (who did the bulk of the excavation) and I were wearing the full gear (suits, face-masks, double gloves, sterilized tools, etc.) to minimize chances of that happening,” explained Dr. King. “Also, I’ve collected samples from everyone who was on the dig team and have sequenced their mtDNA as a precaution so that I can spot any contamination.”
Why Mitochondrial DNA?
Most DNA is found in the cell nucleus. But a small amount is also found in the mitochondria of the cell. It is this DNA that is being used to identify the bones at Greyfriars. Dr. King explained why mtDNA was being used despite its small quantities: “This is the DNA of choice for two reasons. The first of these is that, after death, the usual mechanisms which keep our DNA molecules long and healthy when we’re alive are no longer working and our DNA begins to break down. While there is only one copy of our genomic DNA in each of our cells, there are many, many copies of our mitochondrial DNA; so if anything is going to be left, it will be mtDNA.”
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“The other reason that mitochondrial DNA is so useful in this case is that it’s passed down the female line, from mothers to children (but only daughters pass it on),” said Dr. King. This is particularly important in the case of the Greyfriars skeleton. Without a comparative source of DNA from a modern relative of Richard III, it is unlikely that the search for the king would ever have gotten underway.Decoded Science