Pedigree charts mode of inheritance genetic counseling incomplete penetrance variable expressivity proband affected carrier autosomal dominant autosomal recessive X-linked dominant | X-linked recessive Y-linked inheritance Y-linked mitochondrial inheritance (mtDNA) sporadic product rule sum rule population p+q=1 | Hardy-Weinberg formula p2 + 2pq + q2=1 Hardy-Weinberg equilibrium assortative mating random mating migration genetic drift |