Extraction Protocol: ChelexThis is a fast, cheap, and effective method of DNA extraction. Because this is the first steptowards PCR and amplifying your template DNA, you must maintain excellent sterile techniqueto prevent the contamination of your DNA extractions. Always use a negative chelex control(below) to evaluate your technique during the extraction phase.Work in LOW DNA part of lab.1. Remove premade tubes filled with 300uL 10% Chelexfrom refridgerator. You will need for each sample, plus 1extra for a control. Handle the container with gloves andshake out the number you need into your gloved hand. Donot put extra tubes back into jar.2. Label each Chelex tube to correspond to your samplelisted on your Chelex worksheet. Label the tubes on thecap. Put as much information as you can manage, butkeep labels legible. Adding initials and a date is always agood idea. Avoid labeling on the side of tube as thiswriting can be washed off during the incubation stage.3. Turn on heating block. Set to 95°C. Fill holes withddH2O water.4. Dip forceps into ethanol, then wave forceps through flameof an alcohol burner to ignite. When you are certain thatthe flame on the forceps has extinguished, repeat 2 times.5. Using the sterile forceps, remove a small piece of tissuefrom your sample, uncap the tube of chelex, place samplein the appropriately labeled tube and close lid. The pieceof tissue should be big enough to be visible, but not so bigas to be easily visible. Imagine cutting a 0.2mm section ofa standard staple. This is plenty big. Too much tissue mayinhibit your reactions. The piece of tissue should be aboutas big as a period.6. Repeat (step 5) with each sample in a new Chelex tube, being sure to sterilize forceps 3times between samples (step 4). When finished, make a negative Chelex control bydipping your sterilized forceps into a tube of Chelex slurry. (It may be necessary to wipeexcess tissue from forceps with a kimwipe prior to flame sterilization)7. When finished with all tubes, vortex samples in chelexslurry for 10-15 seconds. Be sure lids are snapped ontightly before begining8. Spin samples briefly (10-15 sec) at high speed in amicrocentrifuge. This step is to ensure that the sample isinside the slurry of Chelex.9. Incubate samples for 20 minutes at 95°C. The blocktemperature may drop slightly when doing this step. Thisdrop is normal. Check tubes while incubating to ensurethat lids have not popped off.10. Vortex samples again for 10-15 seconds (Be careful assteam may pop lid off of centrifuge tube. Hold lidsdown).11. Spin tubes again at high speed in microcentrifuge toensure that all contents are in the bottom of themicrocentrifuge tube.12. Samples are ready to use (or not, see below). ONLYUSE SUPERNATE FOR PCR REACTIONS.CHELEX BEAD WILL INACTIVATE TAQ!Notes:Chelex is notorious for being as fickle as it is cheap and easy. Here are some tips for goodamplifications:1. Sometimes samples work best if used immediately. Sometimes it is better to waitovernight before using them. Experiment and find what works for your species. Resultscan vary by taxa and by individuals.2. When doing initial PCRs, do a serial dilution of template. The amount of a Chelex DNAextraction used in a PCR can be as high as half of the volume of the PCR or as low as 1microliter of a 1:10,000 dilution. I find that 1 microliter of a 1:1 is good for mostapplications, but if your PCR doesn’t work initially, vary template concentration.]Supernate] Chelex3. If you don't get amplifications from your PCR the first time with a Chelex extract, repeatthe vortex, spin, incubate, vortex, spin, sit overnight procedure described above. Oftenthis will make a negative PCR work. Don’t ask me why…
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