Organic Extraction
Definition
A DNA isolation method that uses phenol and chloroform to partition proteins into the organic phase, leaving nucleic acids in the aqueous phase. The gold standard for yield and purity but requires hazardous chemical handling and is largely replaced by solid-phase methods in high-throughput laboratories.
- Reagents
- Phenol and chloroform
- Separates
- Proteins (organic phase) from nucleic acids (aqueous phase)
- Known for
- High DNA yield and purity
- Drawback
- Hazardous chemical handling
- Current status
- Largely replaced by solid-phase extraction
Common questions
Why has organic extraction been largely replaced despite its high yield and purity?+
Phenol and chloroform are toxic and require careful disposal, and the method involves multiple manual liquid-liquid transfer steps that are slow and hard to automate. Solid-phase methods achieve comparable purity with far less hazard and can be run on robotic platforms for high-throughput casework.
Is organic extraction still used in any forensic casework today?+
Yes, it remains a reference or fallback method for challenging samples, such as degraded or low-template evidence, where its high recovery can outperform automated kits, even though it is no longer the default workflow in most accredited high-throughput laboratories.
Related terms
- Chelex Extraction
- A rapid extraction method that uses the chelating resin Chelex 100 to bind divalent metal ions and prevent nuclease activity. Cells are...
- Differential Extraction
- A two-step DNA extraction procedure used when a stain contains both sperm cells and non-sperm epithelial cells. The first step lyses epithelial...
- PCR Inhibitor
- A co-extracted substance that interferes with Taq polymerase activity or primer annealing. Common inhibitors in forensic samples include haemoglobin (from blood on...
- Real-Time PCR Quantification
- A method that measures the concentration of human-specific amplifiable DNA in a forensic extract by monitoring fluorescent signal accumulation during PCR in...
- Solid-Phase Extraction
- A family of methods in which DNA binds selectively to a silica membrane or magnetic bead under high-salt, low-pH conditions, is washed...