Handedness has long been thought to be polygenetic, and Australian researchers have now identified 41 DNA regions that influence left-handedness, and seven that influence ambidexterity.
Via David Evans and Sarah Medland:
Many of the regions of the genome associated with left-handedness contained genes that code for microtubule proteins. These proteins play important roles during development in the migration of neurons and in the ability of the brain to adapt to changes in the environment.
They also found little overlap in left-handedness and ambidexterity, which suggests degree of hand preference and direction of hand preference may involve separate mechanisms.