Ask any parent of twins, and chances are they'll be able to spot which twin is which regardless of their eery resemblance to each other. That's because while your face shape is largely determined by genetics, there certain genes that can still produce subtle differences in our faces.

And according to this new mice study, the answer may lie in our own "junk DNA," which refers to the sequences in a genome that don't produce proteins or have no known biological function.

For the study, researchers managed to identify more than 4,000 small regions in the genome that are likely a type of noncoding DNA called enhancers which serve to amplify the expression of a gene. These regions were also found to be only active when the face of a mouse embryo was being developed. 

The researchers tested this by deleting three of the enhancers in mice before comparing them with normal mice at 8 weeks of age. The enhancer deletion caused a distinct set of differences in facial length, the width of various parts of the face, and the base of the skull or the palate.

Since most of these enhancer sequences are also found in humans, it is likely that they have similar face-shaping functions. By further studying how these enhancers affect our genes, geneticists may be able to look out for any mutations which may play a role in birth defects that cause facial flaws such as clefts of the lip or palate.

[Livescience]