New research shows regardless how similarly they may look, identical twins are not exactly genetically the same.
Icelandic researchers sequenced DNA from 387 pairs of identical twins — those derived from a single fertilized egg — and their close relations.
According to HuffPost, that allowed them to find early mutations that separate identical twins.
A mutation is an alteration in a sequence of DNA that can influence physical features or susceptibility to certain diseases.
On average, identical twins have 5.2 of these early genetic differences, the researchers found.
But about 15% of identical twin pairs have more genetic differences, some of them up to 100.
That could influence why one twin is taller or why one twin is at greater risk for certain cancers.