Chelex 100 as a Medium for Simple Extraction of DNA for PCR-Based Typing from Forensic Material

TLDR

Chelex 100 resin has been developed to extract DNA from forensic samples for PCR. The study compares DQ α genotypes from 84 samples extracted with Chelex versus phenol‑chloroform to assess concordance. The Chelex protocol is a simple, rapid, solvent‑free extraction that requires minimal tube transfers and is compatible with HLA DQ α amplification across diverse forensic sample types. Chelex extraction yields DNA from semen and tiny bloodstains as efficiently or better than proteinase K/phenol‑chloroform, reduces PCR inhibition in bloodstains, and produces DQ α genotypes identical to those obtained by conventional extraction.

Abstract

Procedures utilizing Chelex 100 chelating resin have been developed for extracting DNA from forensic-type samples for use with the PCR. The procedures are simple, rapid, involve no organic solvents and do not require multiple tube transfers for most types of samples. The extraction of DNA from semen and very small bloodstains using Chelex 100 is as efficient or more efficient than using proteinase K and phenol-chloroform extraction. DNA extracted from bloodstains seems less prone to contain PCR inhibitors when prepared by this method. The Chelex method has been used with amplification and typing at the HLA DQ alpha locus to obtain the DQ alpha genotypes of many different types of samples, including whole blood, bloodstains, seminal stains, buccal swabs, hair and post-coital samples. The results of a concordance study are presented in which the DQ alpha genotypes of 84 samples prepared using Chelex or using conventional phenol-chloroform extraction are compared. The genotypes obtained using the two different extraction methods were identical for all samples tested.