mRNA Body-Fluid Profiling
Definition
The RT-PCR-based descendant of Northern blotting: tissue-specific messenger RNA transcripts are reverse-transcribed and amplified from crime-scene stains to identify body fluid of origin. Validated at the NFI (Netherlands), BKA (Germany), and FBI Laboratory for blood, semen, saliva, and vaginal secretion identification.
- Method
- RT-PCR of tissue-specific transcripts
- Predecessor technique
- Northern blotting
- Validated at
- NFI (Netherlands), BKA (Germany), FBI Laboratory
- Identifies
- Blood, semen, saliva, vaginal secretion
Common questions
Why is mRNA profiling preferred over older presumptive chemical tests for body fluids?+
Presumptive tests like the Kastle-Meyer test for blood can cross-react with non-target substances and only give a probable result, while mRNA profiling targets transcripts expressed specifically in one tissue type, giving a molecularly specific identification that presumptive colour tests cannot.
Can mRNA profiling be combined with STR DNA typing from the same stain?+
Yes, laboratories have developed co-extraction protocols that recover both DNA and RNA from a single stain, allowing body fluid identification and donor DNA profiling to proceed from the same sample without needing to split limited evidentiary material.
What is the main technical challenge with using RNA instead of DNA?+
RNA degrades far more rapidly than DNA due to ubiquitous RNase enzymes and environmental exposure, so sample handling, storage, and extraction protocols must be more rigorous to preserve transcript integrity before amplification.
Related terms
- Microarray (Gene Chip / SNP Chip)
- A solid-phase hybridisation platform carrying thousands to millions of oligonucleotide probes at spatially registered positions. Hybridisation of a labelled target simultaneously queries...
- Minisatellite (VNTR)
- A hypervariable genomic locus characterised by tandem repeats of a 10-60 bp core sequence, with the number of repeat units varying between...
- Molecular Hybridisation
- The formation of a double-stranded nucleic acid molecule from two complementary single strands, driven by hydrogen-bond formation between base pairs (A-T, G-C...
- Southern Blot
- A technique (E.M. Southern, 1975) in which restriction-digested DNA fragments are separated by gel electrophoresis, transferred to a membrane, and hybridised with...
- Stringency
- The extent to which hybridisation conditions favour only perfectly complementary probe-target pairs over partially mismatched ones. High stringency (elevated temperature and/or low...
- Western Blot (Protein Immunoblot)
- SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of proteins followed by electrotransfer to a PVDF or nitrocellulose membrane, then antibody-based detection of a specific protein...