The nature of the wide variety of substrates on which forensic biological samples are deposited can create problems for the DNA analyst. For example, the substrate may cause collection problems or it may contain substances that interfere with the Polymerase Chain Reaction (PCR) assay. The main problem is inhibition; the efficiency of amplification of forensic samples is often significantly decreased because of inhibitors present in the sample substrate. Inhibition can result in partial DNA profiles, and in severe instances, false negative reactions.
Even when sample collection and PCR have worked properly, difficulties may arise in the interpretation of samples from multiple donors.
Click here to read more about mixtures in Subject 06, Module 03.
Upon successful completion of this unit of instruction, the student shall be able to:
- Identify potential obstacles in collection, extraction, and amplification
- Describe potential PCR inhibitors
- Identify techniques to overcome inhibition
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