Question: I don't exactly know what you mean when you say sequencing DNA. What does that process involve?

Well I’m not sure how much you already know so I will start with the basics.

All living things are made up of cells. DNA (or genes) are what we all have inside every single one of ours cells. DNA is the chemical inside the cells that carries instructions for making living organisms. Every single living thing on earth from plants, bacteria, humans, fish, all have DNA inside them.

When two animals mate, their offspring will have half their mothers DNA and half their fathers DNA. So every living thing in the world has its own unique DNA pattern (genetic code). As we inherit DNA from our parents we can trace back through history our ancestors and work out who is related to who. For example two brothers will have DNA (genetic codes) more similar to one another than two cousins.

We humans evolved from monkeys so we have more DNA in common with monkeys than we do with say a dolphin. We will have more DNA in common with a dolphin than say a tree because we are more closely related to dolphins than trees.

So what I do in my line of work is I take a sample (skin sample or blood sample if it a larger animal like a fish or mammal and if its a small animal like an insect or bacteria I will just use the whole thing). Then I break open the cells by using chemicals and bashing the cells about in a machine (DNA extraction). Once the cells are broken open the DNA is then released. DNA is so small so I then need to amplify the DNA which means I make lots and lots of exact copies of the DNA. Then I load the DNA sample onto a sequencing machine. DNA is made up of chemicals: adenine (A), thymine (T), cytosine (C), and guanine (G). The sequencing machine will ‘read’ the DNA and give me a genetic code back telling me the order of the chemicals using the first letter of each chemical (e.g. AGGGTCCTATGTTAAC).

As all living things have unique DNA codes I can tell what species something is by the genetic code. For example if I collect a bottle of water and I want to know what bacteria are present in my water I can break open the bacterial cells and sequence the DNA in the water to find out what bacteria are there. That way I can make sure that there are no harmful bacteria in the water that could make us ill.

I hope that helps! Did that make some sense? Let me know if it didn’t and what bits you don’t understand and I will try my best to explain it better.