You Have Some Strange Relatives!

I don't want to be insulting, but you share about half of your DNA with a banana. We have some pretty strange cousins! Our closest relative is the chimpanzee, which shares about 98 percent of our DNA.

Our DNA is unique to us, but it is similar to other animals and plants. Although no other living thing has DNA identical to ours, we do have great similarities.

What is truly amazing is that living things can read each other's DNA code. A bacterial cell can understand and decode human DNA; a horse can understand crab DNA; a fly can understand mouse DNA. We all speak the same genetic language.

The more you think about this the weirder it becomes. Think of something really ugly or horrible, something that scares you, like a spider, or snake, or slug. If you put your DNA into the nucleus of one of its cells it would understand it and decode it and make what your DNA commanded it to make. And the same is true in reverse; your cells could decode spider, or snake, or slug DNA. And it does not have to even be an animal; your cells can read stinging nettle DNA, and slime mould DNA can read yours. We can all read each other's genes. Every living cell on Planet Earth speaks the same biological language.

That's awesome!

This fact is used in medicine. When people suffer from the disease called diabetes they can't control the sugar levels in their blood because they are unable to produce a special chemical, a hormone, called insulin. Scientists can cut out the DNA from human cells that codes for making this substance and then stick it into the DNA of some bacteria. What now happens is staggering.

The bacterium reads the human gene as if it is its own and starts making insulin. In fact the bacterium also divides, multiplying itself, making more and more cells with the human insulin DNA within it. In the end there are lots of these bacterial cells with the human insulin gene spliced into them, and so together they produce lots of insulin, which we use to inject into people with diabetes.

Now for the really bizarre stuff: suppose a gene coding for making an eye was taken out of some mouse cells and put into the cells of a fly larva that would later develop to become a leg.

What would happen?

It sounds like something out of a horror movie - but it has been done, and what happened surprised everyone. The fly did develop an extra eye, yes, an eye on its leg - but the eye was not a mouse eye; it was a fly eye. The fly cells not only read the mouse DNA; they used it to trigger the making of their own type of eye.

This is incredible.

Life is full of mystery.