Did you every wonder: How is our personal identity defined by DNA if we all have the same genes?

Well, it’s because every gene comes in many varieties – they’re called alleles.

Even the tiniest change in the gene makes it a new allele. Sometimes we can predict what that change means, but mostly it requires years of intense study, and many geneticists believe most of the changes that make new alleles don’t actually change the function of the gene at all.

Imagine this: Your putting on your favourite evening dress, comparing every combination of jewelry and make-up for the greatest effect.

Most combinations make little difference. There may be one real show-stopper, but there will be a small number that make your evening a disaster.

Alleles are like that too. It’s that very small number which cause genetic diseases, which range from physical to mental.

So although we all have the same genes, their arrangement and final effect is truly personal. A matter, you could say, of identity.