Family members with eye cataract are shown with a solid left half of the symbol; those with pituitary dwarfism are indicated by a solid right half. Individual IV-1 and IV-5 decide to have a child together. What is the probability of their first child having both eye cataracts and dwarfism? Solution If I-1 (mother) is the carrier for eye cataract and 1-2 (father) is a carrier for pituitary dwarfism, we can see that the first child is unaffected (II-1). Same case we can also find in III-5 (carrier for eye cataract) and III-6 (carrier for pituitary dwarfism) are married, their first child will be uneffected (IV-4). Ans: In the same way if IV-1 (carrier for pituitary dwarfism) marries IV-5 (carrier for eye cataract), the probability of their first child having both eye cataract and pituitary dwarfism will be Zero. Note: Probability is defined as the extent / chance of an event to occur. If the probability is 0 then it indicates that the event is impossible to occur..