Comparison of DNA preservation between ribs and vertebrae.

The choice of skeletal element types and their intra-bone parts is important because of differences in DNA preservation, and this must be considered when sampling bones for DNA testing. When incomplete skeletons are found, ribs and vertebrae have been shown to be the most suitable for genetic identification of bones from the torso. This study compares the preservation of DNA between 12th thoracic vertebrae and first ribs to determine which bone type is more suitable for genetic typing. The study analyzed 35 12th thoracic vertebrae and 29 first ribs from one mass grave from the Second World War with commingled skeletal remains excavated. Bone DNA preservation was estimated by measuring nuclear DNA concentration and its degradation and through short tandem repeat (STR) typing success. Previous studies performed on aged skeletal remains have shown that the DNA content of the first ribs and 12th thoracic vertebrae has high intra-bone variability, and this was considered when sampling the bones. After full demineralization extraction, the PowerQuant System (Promega) was used to measure the quantity and quality of DNA, and the GlobalFiler kit (Applied Biosystems) was used for STR typing. The results showed that DNA yield and degradation and STR typing success exhibited no statistically significant difference between first ribs and 12th thoracic vertebrae, and there was no intra-individual difference when comparing only paired bones from the same individuals. Consequently, with intra-bone DNA variability considered, the first ribs or the 12th thoracic vertebrae can be selected when sampling to genetically identify the skeletal remains of highly degraded torsos. HIGHLIGHTS: The first ribs and thoracic vertebrae are the most suitable bones for sampling from the torso. The proximal part of first rib and posterior vertebral column of the 12th thoracic vertebrae yielded the most DNA. The first ribs were compared with the 12th thoracic vertebrae, and the sampling process considered intra-bone DNA variability. The quality and quantity of nuclear DNA and success of STR typing were measured. The first ribs yielded the same DNA yields as well as STR typing success as the 12th thoracic vertebrae. When only the torso is present, it is not of high importance whether the first ribs or the 12th thoracic vertebrae are collected.