Deoxyribonuclease (DNase)
Definition
An enzyme that cleaves the phosphodiester bonds in the DNA backbone, fragmenting double-stranded DNA into shorter pieces. Bacteria and fungi produce extracellular DNases as part of normal metabolism. High DNase activity in moist biological evidence is the primary enzymatic cause of rapid DNA degradation.
- Function
- Cleaves phosphodiester bonds in DNA backbone
- Source
- Bacteria and fungi (extracellular enzyme)
- Forensic effect
- Primary enzymatic cause of DNA degradation
- Risk condition
- Moist, microbially active biological evidence
Common questions
How does DNase activity affect DNA evidence collection practice?+
Because moisture accelerates microbial growth and DNase release, biological evidence such as blood or tissue is air-dried before packaging and stored cold, which slows microbial activity and enzymatic breakdown, preserving amplifiable DNA for longer.
Does DNase degradation fragment DNA randomly or in a predictable pattern?+
Degradation is generally random along the strand, producing a smear of progressively shorter fragments rather than clean breaks at fixed sites, which is why heavily degraded samples show reduced yield at longer STR loci first.
Related terms
- Chain of Custody
- The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes...
- Cold Chain
- The documented, unbroken sequence of temperature-controlled environments (refrigerated vehicle, controlled intake, laboratory refrigerator or freezer) through which perishable biological evidence passes from...
- Paper Packaging
- The standard packaging material for biological evidence. Paper is gas-permeable: residual moisture evaporates through the packaging after sealing, preventing the humid microenvironment...
- Partial DNA Profile
- A DNA profile in which results were obtained at fewer loci than the full STR panel used. Partial profiles arise from degraded...
- Q10 Rule
- The empirical observation that most chemical and enzymatic reaction rates roughly double for every 10-degree Celsius increase in temperature. Applied to DNA...