understanding punnett squaresneurofibromatosis punnett squareachondroplasia punnett squarehuntington's disease punnett squareheterozygous punnett squarepunnett square examplehomozygous punnett squarehemophilia punnett squarethalassemia punnett squarepunnett square genotypeheredity and punnett squaresmendelian punnett square