Capillary Electrophoresis (CE)
Definition
A separation technique that resolves DNA fragments by size through a polymer-filled glass capillary under an applied electric field. Single-base resolution is achievable under optimised conditions.
- Capillary diameter
- 50 to 100 micrometers (fused silica)
- Detection method
- Laser-induced fluorescence
- Resolution
- Single-base resolution achievable under optimized conditions
Common questions
How does capillary electrophoresis separate DNA fragments?+
CE separates DNA by size using a polymer-filled glass capillary under an electric field. The fragments migrate through the capillary at different speeds based on their size, allowing them to be resolved and sized down to single bases under optimized conditions.
Why is CE used in forensic DNA profiling?+
CE is the standard platform for sizing forensic STR profiles. It uses very high voltage in narrow fused-silica capillaries combined with laser-induced fluorescence detection, delivering the precision needed to match DNA profiles reliably.
What are the key technical features of forensic CE?+
Forensic CE systems use fused-silica capillaries that are 50 to 100 micrometers wide, apply voltages in the kilovolt range, and detect DNA fragments using laser-induced fluorescence. This combination provides the high resolution and sensitivity required for casework.
Related terms
- Agarose
- Polysaccharide gel from seaweed. Large pore size, used for nucleic acids and large proteins. Standard for DNA submarine gels.
- Allelic Ladder
- A multi-allele reference standard containing the full range of known alleles at each STR locus in the panel, co-injected with samples to...
- Drop-in
- Sporadic appearance of a low-level peak not reproducibly present in re-amplifications, typically caused by trace contamination. Distinguished from genuine minor-contributor alleles by...
- Drop-Out
- Failure of a genuine allele to amplify above the analytical threshold, typically due to low or degraded template. Creates apparent homozygosity at...
- Electrophoretic Mobility (μ)
- Velocity of a charged particle per unit electric field, μ = v/E. Depends on charge, size, shape and the viscosity of the...
- GeneMapper ID-X
- Applied Biosystems analysis software for STR genotyping. Current-generation tool used in the majority of US, UK, and Australian forensic DNA laboratories.
- IEF (Isoelectric Focusing)
- Electrophoresis across an immobilised pH gradient. Each protein migrates until it reaches its pI and stops. Very high resolution; used in haemoglobin...
- Immunoelectrophoresis
- A two-step technique: proteins are first separated by electrophoresis in agar gel, then antiserum diffuses from a parallel trough and forms precipitin...
- Isoelectric Point (pI)
- pH at which a molecule (usually a protein) carries zero net charge and stops migrating. The basis of isoelectric focusing (IEF).
- OSIRIS
- Open-source STR analysis software developed by NIST (US National Institute of Standards and Technology), used as an independent or supplementary analysis tool...
- Polyacrylamide (PAGE)
- Cross-linked synthetic gel with tunable, smaller pore size. Used for proteins and small DNA fragments.
- Precipitin Arc
- Curved line of antigen-antibody precipitate that forms at equivalence in immunoelectrophoresis. Shape and position identify the antigen.
Explained in these topics
- Capillary Electrophoresis and Electropherogram InterpretationA separation technique that resolves DNA fragments by size through a polymer-filled glass capillary under an applied electric field. Single-base resolution is...
- Electrophoresis in Forensic Science: High Voltage, Low Voltage and ImmunoelectrophoresisSeparation in a narrow fused-silica capillary (50–100 μm) at very high voltage (kV), with laser-induced fluorescence detection. The platform on which forensic...