microRNA (miRNA)
Definition
Small non-coding RNA molecules of approximately 18-24 nucleotides that regulate gene expression post-transcriptionally. Abundant in blood cells, relatively resistant to degradation compared with full-length mRNA, and detectable by PCR assays with high sensitivity.
- Length
- About 18 to 24 nucleotides
- Function
- Post-transcriptional gene regulation
- Stability
- More resistant to degradation than mRNA
- Detection method
- PCR-based assays
- Forensic use
- Body fluid and stain age estimation
Common questions
Why is miRNA preferred over mRNA for degraded stains?+
Its small size and tight association with protein complexes make it markedly more resistant to the nuclease activity and environmental breakdown that quickly destroy longer mRNA transcripts, so it survives in older or environmentally exposed bloodstains.
How does miRNA help estimate how old a stain is?+
Certain miRNA species degrade at measurable, reproducible rates after deposition, so their relative abundance in a stain can be compared against a calibration curve to place the stain within an approximate age range.
Related terms
- Degradation Index
- A ratio or combination of RNA abundance measurements designed to capture the state of degradation of a sample. Often calculated as the...
- Inter-Individual Variability
- Differences in RNA degradation rate between different donors' blood, arising from variation in RNase activity, blood cell composition, and haematological status. One...
- mRNA (Messenger RNA)
- Transcripts encoding proteins, synthesised in the nucleus from DNA templates and translated by ribosomes. mRNA molecules vary greatly in length (hundreds to...
- RNase
- Ribonuclease enzymes that cleave RNA phosphodiester bonds. Present in blood plasma (RNase A family) and released from cells on death. The activity...
- RT-qPCR
- Reverse-transcription quantitative PCR: a two-step assay in which RNA is first converted to complementary DNA (cDNA) by reverse transcriptase, then amplified and...