Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. matthew has a family history of the condition, although he does not express the trait. jane is an achondroplastic dwarf.
matthew and jane are planning a family of several children and want to know the chances of producing a child with achondroplastic dwarfism. if three children are born to matthew and jane, what are the chances that the first two children will not express the trait but that the third child will be an achondroplastic dwarf.