Evaluation of Mitochondrial DNA Coding Region Assays for Increased Discrimination in Forensic Analysis

• NCJ Number: 221424
• Journal: Forensic Science International Genetics Volume: 2 Issue: 1 Dated: January 2008 Pages: 1-8
• Author(s): Martina Nilsson; Hanna Andreasson-Jansson; Max Ingman; Marie Allen
• Date Published: January 2008
• Length: 8 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: Ireland

Annotation

This study provides results from an extensive investigation of the variation in the mitochondrial coding region among some haplogroups commonly seen among Caucasians (H, U, T, and K).

Abstract

Results show that among Caucasian populations, haplogroup H is the most common and is present at frequencies between 40 and 50 percent. The most common HVI/HVII type is present in approximately 7 percent of individuals of Caucasian origin. Other HVI/HVII types also occur at high frequencies, rendering some individuals indistinguishable by HVI/HVII analysis. Coding region assays were very useful for resolving sequences with identical HVI/HVII regions. The best-performing coding region assay was able to discriminate 46 percent of the resolvable sequences. When nuclear DNA cannot be obtained, sequencing of mitochondrial DNA (mtDNA) is a commonly used alternative for these samples, due to its high DNA copy number per cell. In addition, the mitochondrial genome has a higher nucleotide substitution rate than the nuclear genome, and the two hypervariable regions HVI and HVII, located in the non-coding control region, are dense in polymorphic positions. The extensive sequence variability found within the control region makes this region suitable for routine analysis in human identification. However, due to maternal inheritance and the resulting lack of recombination of this genome, there is a relatively high risk of mtDNA sequence identity by chance. Although a majority of the HVI/HVII mtDNA sequences are found to be unique in a large sample set, several individuals share identical sequences. Mitochondrial DNA is characterized by clusters of closely related lineages, or haplogroups that are distinguished by certain diagnostic polymorphisms. The diagnostic SNPs that define these haplogroups are commonly located in the coding region, and some are more common in certain populations. Data were collected for 495 complete mtDNA sequences. In order to add a local geographic perspective to the evaluation, DNA from 20 individuals of Swedish origin were also sequenced and analyzed. Tables, figure, references