The first thing we do when we receive packages of parasitoids is to look at them under a microscope. As much as we can, we then work out what they are using identification keys.
A lot of parasitoids, particularly the subfamily of wasps we are looking at (the microgastrines) are not yet described by taxonomists. Even for those that are, we’re definitely not experts in every type of wasp! This means that whilst we might be able to work out which family and genus of wasps the parasitoid belongs to, we might not know what species it is. That’s where the DNA comes in!
Getting the DNA out of the wasp
The first step to doing a DNA extraction is to remove the part of the wasp you want to get DNA out of! Often we will just use a couple of legs, so that the rest of the wasp stays intact and we can look at it later.
Once the legs are removed we put them in a small tube and take them to the DNA extraction lab.
We always wear gloves during a DNA extraction, as we don’t want to get any of our skin cells (which are full of OUR DNA) into the tubes and contaminate them.
In the DNA extraction lab, we add something called a lysis buffer, which breaks down the cell walls of the wasp so that we can get to the DNA. We also add an enzyme which starts digesting (breaking down) the proteins, which would otherwise get in the way.
Then we put all the tubes on a heat block, which keeps them nice and warm (55°C) overnight so the lysis and enzyme can do their stuff!
The next day we remove the proteins and any other material that is in our tube, purifying the DNA. We add isopropanol (a type of alcohol) and glycogen. The DNA and the glycogen are insoluble in water, so will separate out, whilst any material left in the tube that is soluble in water will stay in solution. The tubes stay in the freezer overnight, and then we spin them in a centrifuge to make the DNA clump into a tiny ball at the bottom of the tube. The centrifuge (below) spins the tubes really fast, making heavier things (like the DNA) go to the bottom of the tubes.
The last step is to do a wash with ethanol (another type of alcohol) and then add a buffer that the DNA will stay stable in for our future work! Easy as that, we’ve got purified wasp DNA ready to use.
Want to do your own DNA extraction? This is a good version of a simple extraction to use on your own DNA at home!