- Course Introduction
- 01: Evidence & DNA
- 02: Forensic Biology
- 03: DNA Extraction & Quantitation
- 04: DNA Amplification
- 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
Sample Preparation
Home > Other DNA Markers & Technologies > Non-Nuclear DNA Markers > Mitochondrial DNA > Sample Preparation
Mitochondrial DNA methods are useful in analyzing degraded samples and those containing very low quantity of nuclear DNA. mtDNA is present in cells at a much higher copy number than nDNA (as noted in the table/animation above). The increased copy number of mitochondrial DNA per cell increases the concern for contamination introduced in the laboratory. The procedures used in mtDNA laboratories are designed to limit the possibility of contamination.
These procedures include:
- Wearing of special clothing (e.g., face masks, sleeves, hair nets)
- Use of dedicated laboratory equipment and other supplies
- Frequent cleaning and decontamination of laboratory and equipment
- Organization of work flow
- Monitoring of extraneous DNA through controls
Several forensic and ancient remains research laboratories have published cleaning and extraction procedures for recovery of DNA from bones and teeth. The specific cleaning procedures are extremely important. If these specimens are not properly cleaned, external contaminants and potential inhibitors may be extracted with the DNA.20, 21 As described in Subject 3 Module 1, inhibitors may be detrimental to the amplification process.
Published procedures include:22-27
- Rinsing the specimen with double distilled deionized water
- Rinsing with a dilute hypochlorite solution
- Polishing the specimen with a grinding stone followed by water and Bleach rinses
- Exposing the specimen to ultraviolet irradiation
- Vertical sectioning of the tooth’s crown for removal of the dental pulp
Specialized tools are needed for many of these extraction procedures, e.g., a Dremel tool, a MicroMill grinder, a freezer mill, an aluminum oxide wheel, a grinding stone, a mortar, a pestle, a chisel, a hammer, and/or a saw with diamond blade, just to name a few. The extraction of DNA from bones and teeth is a challenging process; many of the challenges can be overcome with the appropriate procedures and equipment.
