Bio-Rad CHEF Mapper® XA System - Manual (Page 62)

Problem Solution
Applications:
Bands smeary or fuzzy 1. Excessive heating. Lower the voltage or ionic
strength of the buffer
2. Improper switch interval (see Section 9.1)
3. Gel percentage too low; increase
4. Sample degraded; impure enzymes, or wash
cycles too short (agarose blocks)
5. Agarose impurities; consult Bio-Rad
6. Sample overload; adjust sample concentration
Large DNAs not resolved 1. Lower the voltage gradient to below 2 V/cm
2. Increase switch time
3. Agarose impurities
High background in lanes 1. Insufficient washing of samples
2. Sample may be contaminated with RNA or
other material
3. DNA concentration too high
Distorted bands 1. Sample contains too high salt or detergent
concentration
2. Buffer breakdown; change every 24 hours
3. Wells were distorted; recast gel
4. Sample plugs were crushed when placed in
wells
5. Pump flow rate too low; check for kink along
tubing
Thick bands 1. Use thinner wells
2. Load less sample
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