gDNA Quality Requirements

Overview

As for all genotyping methods, gDNA quality has a major effect on genotyping data quality. 

There are three key aspects of DNA sample quality: 

1. DNA length and length distribution
2. Absence of nucleases that will degrade your DNA
3. Absence of inhibitory contaminants (often seen as coloured DNA samples).

To address these first two points, we recommend performing gDNA incubation tests of the samples before shipping them to us, even if it is on a subset of the samples. Incubate 2µL of gDNA in 1x restriction enzyme buffer at 37°C for 2 hours and then compare the samples with and without this incubation, in restriction enzyme buffer on a 0.8% 1xTAE agarose gel. Nuclease-free gDNA samples will be essentially unchanged. Samples that show degradation to just short fragments will not perform optimally in DArT services. 

To address this third key aspect of sample quality, we recommend you improve your gDNA extraction process such that the DNA extracts obtained are clear, uncoloured solutions. If this is not achievable we will normally need to perform our additional cleanup method once your samples are received, at extra cost. gDNA derived from museum collections, valuable items and materials that have been in prolonged storage (3.3) 

Good gDNA example

Degraded gDNA examples

gDNA degraded by endonucleases after 2 hours incubation test. The last well is a positive control (PC).

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Please also read how to send Samples from sensitive or valuable material.