Before revision: Discovery The first described occurrence of polar overdominance in sheep was shown after finding that a mutant Callipyge allele must be inherited from the father to cause a condition called muscle hypertrophy.
After revision: Discovery The first described occurrence of polar overdominance in sheep was shown after finding that a mutant allele, called callipyge (after Venus Callipyge), must be inherited from the father to cause a condition called muscle hypertrophy.