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DNA Extraction and Quantitation for Forensic Analysts

Microcentrifuge Tubes with Spin Baskets

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Photo of gloved hand holding a microcentrifuge tube with spin basket
National Institute of Justice (NIJ) (see reuse policy).

Constructed with an open end and a woven end, spin baskets hold a cutting of substrate and are inserted into a common microcentrifuge tube. This allows for the retention of liquid carrying the biological material to be separated from the substrate during centrifugation steps. Any cells that may not be completely freed from the substrate are forced into the tube, along with the excess fluid. Spin baskets may also be used in organic extractions, although their composition prohibits immersion in phenol/chloroform/isoamyl alcohol (PCI).

For example, Promega offers the Differex™ System, which includes a proprietary separation solution and the use of a spin basket, increasing the efficiency of the traditional method of differential extraction from sperm versus non-sperm cells. The procedure begins with Proteinase K digestion to lyse non-sperm cells. The sample and buffer are placed into a spin basket within the tube containing the proprietary solution. This solution is not miscible with the aqueous buffer. Through centrifugation, the sperm cells form pellets, while the non-sperm DNA remains in solution. The difference between this system and routine differential extraction is that the separation solution acts as a selective membrane (without the risk of clogging), which is purported to reduce the chance of sperm loss. After the removal of the solution containing non-sperm DNA, the sperm DNA is isolated using the DN™ System, described later in this module.

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