Tips for Successful Genomic DNA Extraction from Blood Samples

Get helpful tips for DNA extraction from blood samples using the Monarch Genomic DNA Purification Kit

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In the following video, we will share some tips for successful genomic DNA purification from blood samples. In almost all cases, blood samples are collected in a vacutainer containing an anticoagulant to prevent clotting. The Monarch Kit can be used to process blood samples stored in any anticoagulants. As with any DNA isolation, it is important to use the correct amount of starting material. Nucleated blood, such as that of birds and reptiles, is DNA-rich and therefore only a small amount of blood is required. Mammalian blood samples are not as DNA-rich because the red blood cells are not nucleated. Therefore, a greater input amount is required. The storage and lysis conditions of the blood samples play a significant role in the success of gDNA preps. Freshly-drawn blood samples are more difficult to lyse, so when working with fresh samples, we recommend lengthening the lysis time from 5 minutes to 10 or 15 minutes. Fresh samples will typically provide DNA of the largest peak size, but yields may be lower than when using slightly older blood. Samples that are stored at 4-8 °C for 2 – 5 days are easier to lyse and can result in higher yields than fresh blood, but the peak size of the DNA may be slightly lower due to some nuclease activity. It should be noted that storage of blood at 4 °C will lead to sedimentation of cells, so it’s important to resuspend the samples before processing, either by vortexing or inverting thoroughly. Fresh blood samples should not be stored at 4–8°C for longer than a week. Plasma of whole blood is rich in nucleases, which are kept in check as long as leukocytes remain intact. When stored at 4 °C for too long, the leukocytes become unstable and nucleases will degrade the DNA. For unfrozen blood samples, it is important to add RNase A and Proteinase K to the sample prior to adding the lysis buffer, so that these enzymes can quickly degrade the nucleases that are released upon lysis. Frozen blood samples will give gDNA of excellent quality, but it is essential that samples are not thawed before purification. This is because ice crystals damage the leukocyte cell structures during freezing and, upon thawing, nucleases will rapidly degrade the DNA, reducing quality. When working with frozen blood samples, add the RNase A, Proteinase K and lysis buffer to the frozen sample and then incubate immediately at 56 °C; the Blood Lysis Buffer protects the DNA from nucleases as the sample thaws, ensuring that large genomic DNA fragments are obtained. When archiving blood samples, we recommend storage at -80°C. We hope that these tips have been helpful. If you have any questions, our scientists are ready to help. Contact us at info at NEB.com.
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