You might think that identical twins have an advantage when it comes to crime—with the same DNA, who could tell them apart? But new research with a squad of scent-trained Czech police dogs reveals that even identical twins have their own individual smells, even if they live in the same house and eat the same food.
— Read more at Police Dogs Can Tell Identical Twins Apart By Scent at Discover magazine.
Is anyone surprised by this? Isn’t it now common knowledge that identical twins are only absolutely identical in common perception? As soon as the egg splits into two embryos, those embryos start to differentiate…so why is this a surprise?
You’re right. Identical twins only have nearly identical DNA and there are other factors affecting the phenotype (appearance, traits, and apparently smells, etc.) of twins, such as epigenetics and mutations. For example, they don’t have the same fingerprints due to epigenetic differences. In identical twins, the rate of the expressivity of a gene, meaning how much that gene is used to synthesise proteins, varies and this difference causes variant phenotypes. Also, in female identical twins, the deactivation of different X chromosomes may occur, as a result of this the twins can express different phenotypes.
I had really never thought about it either way! I probably would have guessed they had unique smells, but couldn’t swear to it.