A geneticist notices with concern that a striking similarity in appearance exists between his son and a male neighbour. the geneticist would be reassured that he and not the neighbour is the true father of the child if
1.the neighbour and the son have a normal but unusual polymorphic variant of chromosome 9
2.the neighbour\'s blood group is A rh positive and the son\'s is B negative
3. the neighbour has cystic fibrosis
1.F 2. 3.T
