Question: How do you identify the DNA of tiny microscopic plankton and other things like that, they are soooooo small ?

Well that’s why DNA is a better way to study small animals. They are difficult to study by looking at them because they are so small but their genes can tell us a lot about the animal.

DNA is present in every single cell in your body and every living thing on the planet has DNA. DNA is basically the set of instructions that cells use to make an animal (or plant).
Every living thing on earth has a unique DNA code (genetic code). So yours will be different to mine etc. You get your DNA off your parents so half your DNA came from your mum and half your DNA from your dad. I can work out who you are related to based on your genetic code. So your DNA will be more similar to your cousins than to me, but your DNA will be more similar to me than to a dolphins (because we are both human so we are more closely related), your DNA more similar to a dolphin than to a tree because dolphins are mammals and so are you were as a tree is a plant.

DNA is made up of four different chemicals that occur in a different order for every different animal; guanine (G), adenine (A), thymine (T), and cytosine(C). So we use the first letter of the chemical to make up the genetic code. (e.g. AGTTCAAATTTAAGTTTCC). The order of these chemicals is what makes each persons genetic code unique (unless they are an identical twin because then their DNA is identical).

As the DNA is locked away inside the cells of the animal, first, I need to break open the cells to free the DNA. I do this using various chemicals. Once the DNA is free I need to make lots of exact copies of the DNA so I have lots of it to work with. So I use a machine called a PCR machine that makes lots of copies of the DNA. Once I have lots of copies of my DNA I then need I sequence it. I do this on a sequencing machine. A sequencing machine reads the DNA and gives me back a genetic code for that animal. I can then look at this genetic code and work out what the animal is (species), What other species the animal is related to, and I can work out if the animal does various things like break down chemicals, photosynthesizes, etc. All from the genetic code. Most of the time I use the DNA to identify what animals and bacteria are present in the water. Such as rivers or drinking water. Then I can figure out if that water is safe to drink or swim in, etc.

Hope this helps! If there’s any bit you don’t understand let me know and I ill try my best to explain it again. Its all a bit complicated!