DNA Analysis and the Shroud of Turin: Development of a Shroud CODIS

Since its development in the mid 1980s, DNA analysis has become a standard procedure utilized by law enforcement and legal systems in the forensic examination of human remains, and to help establish or exclude a connection to a crime scene. The recent progression of gene amplification and enrichment strategies, together with next generation sequencing techniques, have made the analysis of ancient and degraded DNA samples much more feasible than previously imagined. Human DNA has been isolated from the Shroud of Turin, although the results remain rather limited and controversial. Indeed, it is unknown if such DNA truly originates from blood cells present on the cloth or is the result of contamination from exogenous sources. Here, the potential and limitations of modern molecular biology techniques in the analysis of the Shroud of Turin are reviewed, including the evaluation of both nuclear and mitochondrial DNA. Organization of the human genome: DNA structure and function Deoxyribonucleic acid, or DNA, encodes the information important for the construction of all living things, from simple bacteria to human beings (1,2). Structurally, DNA consists of four bases, or nucleotides, which are symbolized by the letters A,T,C,G. These four bases are the building blocks of DNA. Similar to varying the arrangement of letters of an alphabet to create different words, which are then joined together to form sentences, variation in the number and sequence of the four bases (A,T,C,G) determines the identity and function of specific DNA regions. For example, the DNA sequence TTCGGCCAT would encode a different set of instructions than the sequence CTAGTGTCC or the sequence ATCCTTGCG, and so forth. Essentially two types of DNA sequences exist: (i) genes, which encode specific products necessary for certain cellular functions; and (ii) noncoding segments, that are localized between genes and do not encode specific products. Together, genes and noncoding segments represent a set of instructions that is necessary for the creation and function of a particular organism. This genetic blueprint is referred to as a genome. Sequencing of the entire human genome was completed in 2003, and showed that human DNA contains only 20,000-30,000 genes, a much smaller number than was originally estimated (3,4). Genes account for only about 2% of total human DNA, with the remainder being noncoding sequences. The purpose of noncoding DNA remains to be determined; certain noncoding sequences may function to regulate the expression of specific genes. Other noncoding sequences may be nonessential, i.e. “junk DNA” that serves no identifiable purpose (2-4). Within a cell, both genes and noncoding sequences exist together on DNA strands that are wound around each other in the form of a double helix (Figure 1). Such strands are said to be complementary because the “A” base always pairs with the “T”