The complete sequence of the iceman's mitochondrial DNA

The so-called Tyrolean Iceman or Similaun Man or a'–tzi is perhaps the most famous human mummy in the world. The body was discovered on 19th September 1991 on the Eastern Alps at 3270 m above sea level, near the austro-italian border. Radiocarbon dating of the remains, performed soon after the discovery, indicated an age of 5350-5100 years before present. One of the most interesting features of the find is the exceptional state of preservation of the body and of the pieces of equipment found nearby. This phenomenon is attributed to a spontaneous freeze-drying process. At the time of his death the man was approximately 46 years old and, according to the most recent forensic reconstructions, he was hit by an arrow in the left shoulder then finished off with a mace blow on the face. The first part of the thesis (Paper I-II) is focused on the determination of the mummy's mitochondrial haplogroup. The European mitochondrial DNA is currently divided into nine (H, T, U, V, W, X, I, J, and K) main groups (haplogroups). The K haplogroup, in particular, is composed of two (K1 and K2) subclusters. The present study demonstrates that the Iceman's mtDNA belongs to the K1 subcluster, yet it does not fit any of the three known branches (a, b, and c) into which the K1 subcluster is presently divided. In the second part (Paper III) the complete sequence of the mummy's mitochondrial DNA is determined through a mixed procedure taking advantage of ordinary polymerase chain reaction (PCR) amplification and innovative 454 pyrosequencing technology. This part of the study has required to carry out 236 PCR amplifications and analyze over 42,000 sequences, generated by the pyrosequencing process. The results have revealed the presence of 30 transitions in the mummy's mitochondrial genome compared to the Cambridge Reference sequence (CRS). The third part of the thesis (Paper IV) is devoted to the characterization of post-mortem damage in the Iceman's mitochondrial DNA with a particular emphasis on the so-called Type 1 (A.G/T.C) and Type 2 (C.T/G.A) damage. The results demonstrate that Type 2 miscoding lesions represent the overwhelming majority (88%) of damage in the Iceman's DNA. Type 1 miscoding lesions, on the other hand, are relatively rare and seem to arise from polymerase errors.