In Mendelian genetics the law stated that each organism inherited has of its genetic material from one parent and half from the other.  A mendelian trait that I chose was dimples.  Dimples are a very common thing to see in someone but do we know what they even are?  Dimples are actually genetic defects that are caused by shortened facial muscles.  A variation in the structure of the facial muscle may also cause dimples.  This fault happens during the embryonic development.  Usually dimples are present on both cheeks, a single dimple is very rare.  Having dimples is dominant over not having dimples.

sources: https://sites.uni.edu/walsh/genetics.html, http://study.com/academy/lesson/mendelian-non-mendelian-traits-in-humans-definition-list.html