Terra Direct PCR Polymerase Mix contains an optimized DNA polymerase that allows for direct amplification from a tissue source or crude extracts, without the need for DNA purification. It can amplify DNA targets up to 4 kb as well as difficult templates (including those with a GC content greater than 70%)—and it enables DNA amplification in the presence of PCR inhibitors, growth serum, and other source-material components.

Comparison with competitor PCR enzymes

Terra Direct PCR Polymerase Mix demonstrates an exceptional ability to amplify GC-rich targets and relatively long (4 kb) targets from a crude extract containing human nail DNA.

Terra Direct PCR Polymerase Mix (Panel A) was able to successfully amplify all of the samples. The PCR enzyme from Company A (Panel B) was unable to amplify any of the samples, except for slight amplification of one AT-rich sample (Panel B, Lane 4). The PCR enzyme from Company B (Panel C) was unable to amplify any of the GC-rich samples (Panel C, Lanes 3, 6, and 9) and exhibited diminished performance in amplifying targets as target length increased (Panel C, Lanes 2, 5, and 8).

*UCRchr9 = Chromosome 9 AT-rich noncoding region.
**UCRchr11 = Chromosome 11 AT-rich noncoding region

This experiment demonstrates that Terra Direct PCR Polymerase is a good choice for analyzing extremely tough, hard-to-lyse tissues such as human nails, which are frequently the subject of forensic analysis. Terra was able to amplify gene fragments from GC-rich templates up to 4 kb in length. In contrast, the polymerase from Company B failed to amplify gene fragments containing over 50% GC, while the polymerase from Company A provided poor or no amplification, except for one AT-rich sample.

A crude extract containing human nail DNA was prepared by adding 44 μl of SimplePrep reagent mix (not sold in the U.S.) to a 5-mg human nail sample and treating it according to the standard SimplePrep protocol. 2.5-μl aliquots of the human nail DNA extract were then used as the template in a 25-μl reaction volume to amplify different target gene fragments ranging from 1–4 kb in length and with 26–72% GC content, using Terra Direct PCR Polymerase Mix or inhibitor-resistant PCR enzymes from Companies A and B as shown in the table above. Amplification reactions were performed with each enzyme according to the manufacturer’s instructions, and 3-μl samples of each amplification reaction were analyzed on an agarose gel as shown in the figure above.

The PCR reactions using Terra Direct PCR Polymerase Mix were performed according to the following program: