- Course Introduction
- 01: Evidence & DNA
- 02: Forensic Biology
- 03: DNA Extraction & Quantitation
- Quantitation
President's DNA Initiative
-
Advancing Justice Through DNA Technology
-
Advancing Justice Through DNA Technology
DNA Analyst Training
Overview
Home > DNA Extraction & Quantitation > Quantitation > Overview
Current forensic DNA analysis uses polymerase chain reaction (PCR) based short tandem repeat (STR) testing. Many laboratories use commercially available STR amplification kits. Depending on the kit and reaction volume, the optimal concentration of input DNA will be in the range of 0.5ng – 2ng. Adding too much or too little DNA to the amplification reaction can result in problems in the analysis.
Click here to read more about PCR in Subject 01, Module 02.
In addition to the need for amplification optimization, quantitation of samples is a requirement of the QAS. Standards 9.3 and 9.4 require forensic laboratories to use a quantitation method that is specific to human DNA.
The quantitation process also serves as a quality control and/or troubleshooting procedure. If the STR results are not concordant with those from the quantitation, it may be an indication of a problem such as inhibition, sample switching, or contamination.
Methods
Commonly used quantitation methods include the following:
- Yield gels
- Spectrophotometry
- Fluorometry
- Slot blot hybridization
- AluQuant®
- Quantitative PCR (qPCR)
AluQuant® and Quantitative PCR are the most recent techniques and are becoming more widely used.
