Jason Williams, DNA Learning Center, shows how to prepare an animal or plant sample for DNA isolation.
To begin the protocol, first you need to get a sample of the individual things that you’ve collected. In this case, I have a broad leaf from a maple tree, I have some salmon that’s here, and I have some insects, which are probably crickets. So, what I’ll need is one tube that I’ve labeled for each one of my samples. When you label your samples, and I’m just going to use a Sharpie, give them the designation – I’m calling this one Sample 1 – I’m giving it a date that I’ve actually collected it on or processing it on, and I want to label it on the side as well as the top of the tube just so I can always be sure.
Now when you collect your sample for DNA extraction or when you actually take a small piece of it, less is actually more. It’s actually very important to get a small amount of the sample. For a leaf what we can use is actually a blue pipette tip; this is a P1000 tip, and we can actually use it to make a cutout of the leaf, and really what you’re going for is a very, very small section, so I’m just going to take that. And when you use the tip you actually get a nice round cutout, and I’ll use the forceps to grab this out of the pipette tip.
Now working with fish or other things, such as insects, you’re looking for about 10 to 20 mg, which is a very, very small amount of sample. To illustrate with this piece of salmon, I’m just going to take the scissors, take my forceps and actually cut off a very, very small amount. It’s a little bit less than the size, perhaps, of a pencil eraser, and it’s just that amount that you need in order to get quite a bit of DNA from. I’ll take this, put it into my tube, and of course I want to make sure that I label my tube so that I don’t forget what sample this is.
In some cases, when doing DNA barcoding, you’re actually going to be the author of the barcode. What that means is that not only did you collect DNA and sequence it in order to obtain the DNA barcode sequence, but that you preserved the specimen so that other scientists could study it. What that means is that when you’re collecting a specimen like this cricket, you’re not going to damage the whole insect; you actually want to take just a small amount so that it’s actually identifiable by traditional taxonomy methods. So in this case, we’re just going to take a leg from this cricket, and the rest we can pin and label and store so that we can be the author of the barcode. Here I have a small amount, and that’s really just enough for us to do the DNA barcoding with.
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