What is the condition characterized by hairy pinna of the ear, where all sons show the trait if the father has it?

• A. Hypertrichosis
• B. Color blindness
• C. Cystic fibrosis
• D. Huntington's disease

Answer: (A)

The correct answer is hypertrichosis, which is a condition characterized by excessive hair growth in abnormal areas of the body, including the ears. In this specific instance, the mention of "hairy pinna of the ear" refers to the hair growth on the outer ear, a classic manifestation of hypertrichosis.

The pattern of inheritance described—where all sons of an affected father also exhibit the trait—suggests a Y-linked inheritance pattern. This is because Y-linked traits are passed directly from father to son. Hypertrichosis is one of the few traits that can demonstrate such a paternal transmission pattern, as it can be seen in certain familial forms of the condition.

Other options do not fit this description. Color blindness typically follows an X-linked recessive inheritance and is not exclusively passed from father to son. Cystic fibrosis is an autosomal recessive condition, meaning a child would require two copies of the mutated gene to express the phenotype, which wouldn't guarantee that all sons exhibit the trait if the father is affected. Huntington's disease is an autosomal dominant disorder, allowing for the possibility of affected individuals to pass the condition to offspring, but it doesn’t follow a simple paternal transmission as described in the question.

Thus, hyper