This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'An affected male infant born to normal parents could be an example of all of the following, except: \nSelect and explain. \nA. An Autosomal dominant disorder, B. An Autosomal recessive disorder, C. A polygenic disorder, D. A veically transmitted disorder', 'role': 'user'}, {'content': "Answer: A \nExplanation: A i.e. Autosomal dominant disorder Autosomal dominant disease cannot occur in offspring of an unaffected individuals. Because the allele is dominant it will always express phenotypically (clinically) and hence both parents can't be normal in autosomal dominant disorders even if they have a single abnormal gene.", 'role': 'assistant'}]