Degradation Index
Definition
A ratio or combination of RNA abundance measurements designed to capture the state of degradation of a sample. Often calculated as the ratio of a more-stable species to a less-stable one, or of intact transcript to fragmented transcript. A high degradation index indicates a more degraded sample.
- Field
- RNA/mRNA forensic analysis
- Basis
- Ratio of stable to less-stable RNA species
- Interpretation
- Higher index means more degraded sample
Common questions
What does a degradation index actually estimate about a stain?+
It approximates how much time or environmental exposure has degraded the RNA, which researchers use as one input toward estimating how old a biological stain is.
Why use a ratio rather than a single RNA measurement?+
A ratio of a more-stable to a less-stable species cancels out variation in total RNA quantity between samples, so the value tracks degradation state rather than simply how much material was recovered.
Related terms
- 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...
- microRNA (miRNA)
- 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...
- 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...