Slot blot hybridization was the most commonly used method until recently. The majority of laboratories used the commercially available QuantiBlot® kit, which employs the following procedures:
- Extracted DNA is denatured and the single-stranded DNA is bound to a positively charged nylon membrane.
- After the DNA is bound to the membrane, a probe complementary to the D17Z1 locus (present in high quantities in higher primates) is applied and allowed to hybridize to the DNA.
- The hybridized complex is detected by one of several methods.04
- The amount of DNA in the sample is estimated by comparison of the density of the band or bands observed to that of the standards.
Detection methods include:
- Colorimetry, usually employing tetramethylbenzidine (TMB), which yields a blue color when oxidized by hydrogen peroxide.
- Chemiluminescence, for example ACES™ (Gibco BRL) and™ (Amersham Biosciences). The chemiluminescent reactions cause the release of photons that are captured on film or a digital imaging device. Chemiluminescence is more sensitive than colorimetry and can detect down to 10 to 20 pg of DNA.05
Additional Online Courses
- What Every First Responding Officer Should Know About DNA Evidence
- Collecting DNA Evidence at Property Crime Scenes
- DNA – A Prosecutor’s Practice Notebook
- Crime Scene and DNA Basics
- Laboratory Safety Programs
- DNA Amplification
- Population Genetics and Statistics
- Non-STR DNA Markers: SNPs, Y-STRs, LCN and mtDNA
- Firearms Examiner Training
- Forensic DNA Education for Law Enforcement Decisionmakers
- What Every Investigator and Evidence Technician Should Know About DNA Evidence
- Principles of Forensic DNA for Officers of the Court
- Law 101: Legal Guide for the Forensic Expert
- Laboratory Orientation and Testing of Body Fluids and Tissues
- DNA Extraction and Quantitation
- STR Data Analysis and Interpretation
- Communication Skills, Report Writing, and Courtroom Testimony
- Español for Law Enforcement
- Amplified DNA Product Separation for Forensic Analysts