Abstract
Forensic DNA profiling utilizes autosomal short tandem repeat (STR) markers to establish identity of missing persons, confirm familial relations, and link persons of interest to crime scenes. It is a widely accepted notion that genetic markers used in forensic applications are not predictive of phenotype. At present, there has been no demonstration of forensic STR variants directly causing or predicting disease. Such a demonstration would have many legal and ethical implications. For example, is there a duty to inform a DNA donor if a medical condition is discovered during routine analysis of their sample? In this review, we evaluate the possibility that forensic STRs could provide information beyond mere identity. An extensive search of the literature returned 107 articles associating a forensic STR with a trait. A total of 57 of these studies met our inclusion criteria: a reported link between a STR-inclusive gene and a phenotype and a statistical analysis reporting a p-value less than 0.05. A total of 50 unique traits were associated with the 24 markers included in the 57 studies. TH01 had the greatest number of associations with 27 traits reportedly linked to 40 different genotypes. Five of the articles associated TH01 with schizophrenia. None of the associations found were independently causative or predictive of disease. Regardless, the likelihood of identifying significant associations is increasing as the function of non-coding STRs in gene expression is steadily revealed. It is recommended that regular reviews take place in order to remain aware of future studies that identify a functional role for any forensic STRs.
Highlights
Short tandem repeats (STRs) are short repeated sequences of DNA (2–6 bp) that account for approximately 3% of the human genome (Lander et al, 2001)
Schizophrenia was the trait most frequently described with a total of 11 studies reporting data on 14 different polymorphisms potentially associated with eight loci
The intronic short tandem repeat (STR) TH01 had the greatest number of studies with reports describing traits potentially linked to 40 different genotypes
Summary
Short tandem repeats (STRs) are short repeated sequences of DNA (2–6 bp) that account for approximately 3% of the human genome (Lander et al, 2001). There is increasing evidence, that non-coding DNA sequences such as STRs may be involved in gene regulation via various mechanisms, being associated with phenotype (Sawaya et al, 2013; Chen et al, 2016). Forensic STRs and Phenotype tetranucleotide STRs—TH01, vWA, FES/FPS, and F13A1 (Kimpton et al, 1994). These markers were deemed suitable for PCR amplification due to their simple repeat sequences and their propensity to display regularly spaced alleles differing by four bases; the quadruplex system did not offer a high level of discrimination. Two of the markers initially selected by the FSS (vWA and TH01) were included within the core CODIS set, whereas FES/FPS and F13A01 were eventually discarded due to low levels of polymorphism. The DNA Analysis Backlog Elimination Act of 2000 reaffirms that the markers used for forensic applications were selected because they are not known to be associated with any known physical traits or medical characteristics
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