Organic Extraction of Nucleic Acids Using Ethanol Precipitation or Microcon® Centrifugal Filter Purification Methods

The use of organic solvents to separate nucleic acids from other cell components is a common practice among many scientific fields, including molecular biology and biochemistry. The advantage of performing organic extractions in forensic DNA analysis is the ability to purify DNA from heavily degraded or inhibitory sample types, such as skeletal remains. These sample types require special care to ensure that the DNA is contaminant-free since they often contain PCR inhibitors that negatively impact downstream DNA analysis, resulting in unobtainable or uninterpretable short tandem repeat (STR) profiles. Purification of DNA after an organic isolation procedure is essential for improving the likelihood of obtaining valid STR profile from a challenging evidence sample. This chapter describes the methodology for extracting and purifying DNA from various types of challenging samples that are often encountered in forensic casework.