Answer:
The probability of the next child showing clinical signs of the disease is 1/4.
Explanation:
The above question states that Robin is affected by a mutation. This mutation may or may not be passed on to Robin's children, since the mutation is linked to a genetic factor, however, as the father of Robin's children does not have the mutation, the probability that these children will inherit the Robin mutation is 1/2 and the probability of these children presenting with the mutation symptoms also by 1/2, as presented in the question. The heritability of the mutation and its presentation of symptoms are mutually independent events. For this reason, to know the probability of Robin's next child presenting the clinical signs of the disease, we must multiply these two probabilities. The result will be 1/4.