Question

which genetic disease never has healthy carriers?
○ sickle-cell anemia
○ huntington disease
○ cystic fibrosis
○ tay-sachs disease

Explanation:

• Sickle - cell anemia: It is an autosomal recessive disorder. Carriers (heterozygotes) have some normal and some sickle - shaped red blood cells and are generally healthy (they have sickle - cell trait).
• Huntington disease: It is an autosomal dominant disorder. If a person has the mutant allele (even as a heterozygote), they will develop the disease. There are no healthy carriers. A person either has the disease (if they have the mutant allele) or is normal (if they have the normal allele).
• Cystic fibrosis: It is an autosomal recessive disorder. Carriers (heterozygotes) are healthy.
• Tay - Sachs disease: It is an autosomal recessive disorder. Carriers (heterozygotes) are healthy.

Answer:

B. Huntington disease