A Review of Extended STR Loci and DNA Database

Abstract

DNA typing is the typical technology in the forensic science and plays a significant role in the personal identification of victims and suspects. Short tandem repeat (STR) is the short tandemly repeated DNA sequence consisting of 2~7 bp DNA units in specific loci. It is disseminated across the human genome and represents polymorphism among individuals. Because polymorphism is a key feature of the application of DNA typing STR analysis, STR analysis becomes the standard technology in forensics. Therefore, the DNA database (DNA-DB) was first introduced with 4 essential STR markers for the application of forensic science; however, the number of STR markers was expanded from 4 to 13 and 13 to 20 later to counteract the continuously increased DNA profile and other needed situations. After applying expanded STR markers to the South Korean DNA-DB system, it positively affected to low copy number analysis that had a high possibility of partial DNA profiles, and especially contributed to the theft cases due to the high portion of touch DNA evidence in the theft case. Furthermore, STR marker expansion not only contributed to the resolution of cold cases but also increased kinship index indicating the potential for improved kinship test accuracy using extended STR markers. Collectively, the expansion of the STR locus was considered to be necessary to keep pace with the continuously increasing DNA profile, and to improve the data integrity of the DNA-DB.