This was originally a guest post on The Trenches of Discovery. Thanks, Shaun!

One out of every 8,000 humans is born with some of their internal organs on the wrong side of their body, a condition which can have serious medical consequences. Although we’re usually described as symmetric, that’s only superficially true. Like other vertebrates, we look symmetric from the outside but our internal organs show left-right asymmetry; unless you happen to be a Time Lord, you have only one heart which is normally located on the left side of your chest.  Changes to the organization of the internal organs can lead to cardiac defects, misalignment of the bowel and other serious problems.  Many genes are known to play a role in establishing this asymmetry, but we still don’t fully understand its evolutionary and developmental origins.  Earlier this year, a paper published in the journal PNAS described how this asymmetry is established by  subcellular components early in embryonic development.

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