Isolating DNA
*For isolating genomic and plasmid DNA from cells and tissues, use fresh samples or samples that have been stored at or below -70°C. This reduces nuclease activity.
*For blood preparations, use fresh blood. If the blood is stored, it shouldn't be for more than two days at room temperature, one week at 4°C, or one month at -20°C, and even then DNA yield will still be reduced.
*Collect blood samples in tubes containing heparin as an anticoagulant may disrupt PCR work later. Try to use EDTA instead.
Storing DNA
*For genomic DNA, storage at -20°C can cause shearing, so store it at 4°C.
*For plasmid DNA, 4°C storage is good for the short term and -20°C for the long term.
*Plasmids that are used for transformation should be stored at 4°C to avoid nicks.
*Store modified DNA at 4°C.
Dissolving DNA
*Dissolve DNA in a Tris buffer (such as a 10 mM, pH 7-8 buffer).
*If it doesn't dissolve well, gently invert and/or tap the tube several times. Alternatively, leave it overnight at 4°C. Do not vortex genomic DNA!
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When doing a miniprep, instead of spinning for 1 min at every step, you can centrifuge the column for 15 s, rotate the column by 180 degrees, and follow with another 15 s of spinning. This way you can save a lot of time, and the results are as good.
When doing a miniprep which uses a filter system, the DNA at the end is incubated with water/buffer before the final spin-down. More DNA is eluted when they are incubated at 37°C.
When spinning down DNA or RNA into a pellet, which is hard to see, place the hinge of the microtube towards the outer edge of the centrifuge, so you know where to look for the pellet each time.
When you use ethanol to clean your DNA/RNA pellet, try repeating the spin step after you remove the ethanol supernatant.