NCJ Number
231568
Journal
Forensic Science International: Genetics Volume: 4 Issue: 4 Dated: July 2010 Pages: 244-256
Date Published
July 2010
Length
13 pages
Annotation
This paper describes the development of a messenger RNA (mRNA) multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) system that can detect circulatory blood, menstrual blood, saliva, and semen (with and without spermatozoa), along with three housekeeping genes, in the course of co-isolating nuclear DNA for routine profiling.
Abstract
Under current methodology, DNA profiling can identify an individual from a sample of biological material, but it does not identify the body fluid or tissue source from which the DNA profile originated. The mRNA multiplex definitively identified circulatory blood, menstrual blood, semen, and saliva in forensic casework samples while co-extracting the nuclear DNA for profiling the donor. When mixtures of body fluids from different individuals are present, this technique can more accurately and easily predict their relative ratios without attempting to interpret their ratios from mixed DNA profiles. Although different body fluids have different RNA concentrations, the stochastic amplification effects seen in DNA STR profiling are not as prevalent in the mRNA multiplex. This may be due to the lack of competition between primers for their target sequences, or may reflect the multiple nature of the transcripts compared to a single gene copy, which may assist in producing a less variable mRNA component ratio in these mixed samples. This may be further exacerbated by stochastic variation between heterozygote peaks at each DNA locus. Further work on mixed samples is thus required, and the relative contribution of housekeeping genes to these samples is needed in order to inform interpretative guidelines. An additional consideration is the number of markers that should be included for each body fluid. The authors advise that when coupled with existing screening tests, a single marker is sufficient to confirm the presence of a particular body fluid, providing that the marker used is specific. 2 tables, 10 figures, and 33 references