Dr Robin Cotton discusses the makeup of DNA

Robin:
OK, I'll try to start and Andy can pick up at some point. If you had some biology, this will seem a little bit too easy, and if you haven't had any you have a lot of interesting stuff in store for you.

So each of us, our bodies are made up of cells, and the cells have basically an outer portion called the cytoplasm and an inner portion called the nucleus and inside the nucleus are 46 chromosomes and if you've had a biology class you've probably seen pictures of 46 chromosomes in your book. These chromosomes, each one of them is made up of DNA and you got half of those chromosomes from your mother and you got the other half from your father so if there's something about any of them you that don't like you only have those two parents to blame - it's their fault that you've got some characteristic that you're not happy with - and it's that DNA that we study. And there's really two more things that you would need to understand to think about DNA testing and that is for human beings, of which we all are, more than 99% of our DNA is the same. So while we have different hair colour, and different skin colour and different eye colour, almost all of our DNA is the same because our bodies all function in the same way. What DNA testing for forensics does is look at that tiny fraction that's different but we aren't at this time looking at the part that gives us different physical characteristics. We're looking at parts of the molecule that are different in other ways and when you look at all those differences and you line all those differences up in a row, you can tell one person from another.

More than 99% is the same so we're basically all one huge family.