A twin thing

Dannielle and Prue are identical twins. However, they have a genetic difference that has helped lead Austin Health's world-leading epilepsy specialists Professors Sam Berkovic and Ingrid Scheffer to a scientific breakthrough: Dannielle has a severe form of epilepsy called Dravet syndrome and Prue doesn't.

"We wondered how this might have happened and when it might have occurred," Prof Berkovic said during an interview with ABC Catalyst for a special episode on research into twins.

"We looked at five tissues in both girls and we found that the mutation was present in all five tissues in Dannielle, but not present in any of Prue's tissues. So that tells us that the mutation, the abnormality in the gene, occurred after twinning, said Professor Scheffer.

"The identical twins split and then Dannielle developed the mutation."

It was a discovery that profoundly changed the scientific understanding of epilepsy, and inheritable conditions generally: that genetic mutations can occur not just in the original sperm or egg, but also very shortly after fertilisation.

"There's no way that somebody could have inferred that from studying just single individuals - that was the beauty of twins," said Prof Berkovic.

This year, Twins Research Australia celebrates its 35-year anniversary and counts Professor Berkovic and Sheffer's research amongst the five most significant discoveries to come from its database.

You can watch the Catalyst twins research special on iview.