title: Effects of humic acid on DNA quantification with Quantifiler® Human DNA Quantification kit and short tandem repeat amplification efficiency.
abstract: Correct DNA quantification is an essential part to obtain reliable STR typing results. Forensic DNA analysts often use commercial kits for DNA quantification; among them, real-time-based DNA quantification kits are most frequently used. Incorrect DNA quantification due to the presence of PCR inhibitors may affect experiment results. In this study, we examined the alteration degree of DNA quantification results estimated in DNA samples containing a PCR inhibitor by using a Quantifiler® Human DNA Quantification kit. For experiments, we prepared approximately 0.25 ng/μl DNA samples containing various concentrations of humic acid (HA). The quantification results were 0.194-0.303 ng/μl at 0-1.6 ng/μl HA (final concentration in the Quantifiler reaction) and 0.003-0.168 ng/μl at 2.4-4.0 ng/μl HA. Most DNA quantity was undetermined when HA concentration was higher than 4.8 ng/μl HA. The C                 (T) values of an internal PCR control (IPC) were 28.0-31.0, 36.5-37.1, and undetermined at 0-1.6, 2.4, and 3.2 ng/μl HA. These results indicate that underestimated DNA quantification results may be obtained in the DNA sample with high C                 (T) values of IPC. Thus, researchers should carefully interpret the DNA quantification results. We additionally examined the effects of HA on the STR amplification by using an Identifiler® kit and a MiniFiler™ kit. Based on the results of this study, it is thought that a better understanding of various effects of HA would help researchers recognize and manipulate samples containing HA.
authors.affiliation: Department of Forensic Medicine, College of Medicine, Seoul National University, 28, Yongon-Dong, Chongno-Gu, Seoul, 110-799, South Korea.
authors.forename: Seung Bum
authors.initials: SB
authors.lastname: Seo
authors.forename: Hye Young
authors.initials: HY
authors.lastname: Lee
authors.forename: Ai Hua
authors.initials: AH
authors.lastname: Zhang
authors.forename: Hye Yeon
authors.initials: HY
authors.lastname: Kim
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Shin
authors.forename: Soong Deok
authors.initials: SD
authors.lastname: Lee
mesh_terms: D004247:DNA / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D053803:Forensic Genetics / Q000379:methods*; D006801:Humans; D006812:Humic Substances; D018895:Microsatellite Repeats / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results
chemical_list: D006812:Humic Substances; D011933:Reagent Kits, Diagnostic; D004247:DNA