- 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
Reagents and Consumables
Home > DNA Amplification > Contamination > Sources > Reagents and Consumables
Reagents and consumable supplies can introduce exogenous DNA into the analysis process. Negative controls and reagent blanks will assist in detecting contamination associated with reagents. However, instances of contamination introduced by consumables (e.g. plastic ware, pipette tips) are commonly single tube events and may or may not be detected through the use of controls. 01-04
Reagent contamination is generally more easily detected than that from consumable products. Negative controls and reagent blanks provide a good way to monitor reagent contamination that can adversely affect an entire analysis batch. This is not true for contamination events from consumable products. These are usually single tube events and the level of contamination is low. This type of event is primarily detected in negative controls, reagent blanks, and evidentiary samples with low levels of DNA.
A growing concern in the forensic science community is the possibility that consumables, namely plastic ware, may be contaminated during the manufacturing and/or packaging process. In general, laboratories routinely purchase sterile consumables and have thought them to be free of DNA. However, contamination events have shown that these sterilized products can carry DNA from individuals working in the manufacturing and/or packaging process.
The Forensic Science Service (FSS) has reported incidents of casework-related STR contamination from staff of plastic ware manufacturers.05 Investigations carried out by the FSS prompted the novel establishment of a vendor database consisting of DNA profiles from individuals employed by various vendors of consumable products. The database has subsequently sourced unknown profiles developed in the laboratory to the manufacturing process.
Click here to visit the Forensic Science Service website.
Note: |
The names of the individuals are not included in the vendor database maintained by the FSS. |
The first incident in the United States was reported after DNA profiles were uploaded into the Combined DNA Index System (CODIS) and subsequently linked multiple crimes across multiple states. After it was determined that the FSS had also observed this same profile (with SGM+) on more than one occasion, it was believed that the profile must have originated from a consumable used in the analysis process.
