- Course Introduction
- 01: Evidence & DNA
- 02: Forensic Biology
- 03: DNA Extraction & Quantitation
- 04: DNA Amplification
- Overview
- Introduction
- Amplification
- Primer Design
- Primer Length
- Primer Melting Temperature
- Primer Annealing Temperature
- Values for Tm
- Maximum 3′ Stability
- GC Content Percentage
- No Secondary Structures
- No Self-complementarity
- No Complementarity To Other Primers
- No Long Runs With The Same Base
- Distance Between Two Primers On Target Sequence
- Plateau Effect
- Thermal Cyclers
- Thermal Cycling Parameter and Optimization
- Works Cited & Online Links
- Locus Selection
- Multiplexing
- Contamination
- Overview
- 05: Amplified DNA Product Separation
- 06: STR Data Analysis & Interpretation
- 07: Population Genetics & Statistics
- 08: Communicating Results
- 09: Other DNA Markers & Technologies
- Course Resources
- Laboratory Training Manual
President's DNA Initiative
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Advancing Justice Through DNA Technology
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Advancing Justice Through DNA Technology
DNA Analyst Training
Identify Problem
Home > DNA Amplification > Contamination > Corrective Action > Identify Problem
Step One
If contamination is suspected, the first step of the investigation should be to determine where the contaminant profile has arisen. In many cases, it can be traced back to a particular step in the analysis by working backwards in a step-by-step process.
Click here to view an animation on identifying the problem.
It is important to compare the contaminant profiles to:
- Other samples from the same batch
- Samples from other batches processed in the same timeframe
- Staff profiles
- Previously detected contaminant profiles
- Other persons involved in the collection and handling of the evidence
If the profile contains too few alleles to effectively screen against the above, consideration can be given to boosting the signal strength by using one or more of the following:
- Amplifying additional extract
- Extending the injection time
- Concentrating the extract or amplicon
- Increasing the number of PCR cycles
These troubleshooting procedures should not be used for processing, interpreting, or reporting samples unless validated by the laboratory.
