Can you really study human disease in fish?

Yes! Because fish and humans aren't really that different when you look closely - especially when you look really closely, such as at their DNA.

Building on Charles Darwin’s pioneering insights, we now appreciate the remarkable similarity that exists between the genetic codes of different species.

(Need a recap on genes and DNA? Click here)

It's often surprising to find out how many genes are shared between humans and other animals, but as we learn more about how animals are built it makes more and more sense.

Although humans may appear to be very different to mice, flies, chicks or fish, the reality is that they're not that different at all. All of them have two eyes, a mouth, and a gut, for a start. And when we look closer - at all the cells inside them - there really are more similarities than differences.

To make an eye requires the information stored in many different genes, but since your eyes and those of many other animals work in much the same way the genes involved are pretty much the same. Only subtle changes in the genetic code are necessary to create the differences between them.

This similarity between the genes of different organisms, which scientists call conservation, or genetic homology (from an ancient Greek word meaning 'to agree'), is the fundamental reason why we can use fish to learn about human diseases.

In other words zebrafish can be used as a model organism.