DNA Isolation Step 1: Preparing the Sample

DNA Isolation Step 1: Preparing the Sample


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.

10 thoughts to “DNA Isolation Step 1: Preparing the Sample”

  1. he used the same scissors on the meat on the insect, isn't that cross contamination in terms of the salmon DNA will be in the cricket DNA sample,

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