DNA Science

Quantitation

This process is carried out to ensure that the optimal amount of DNA is used for PCR. Too little DNA will cause under amplification, resulting in a weak or no profile. Whereas too much DNA will cause over amplification, resulting in a profile showing pull up, distortion and a noisy background.

For Spec and major crime work, a dot blot method involving hybridisation of a probe to the sample DNA, coupled with a chemiluminescent reaction was used until August 2004. The probe is specific for human DNA so we can obtain a more accurate quantification score, as samples may be contaminated with bacterial, fungal or non-human DNA. The Major Crime team still uses the dot blot method for some samples and RT-PCR for others.