Autosomal recessive disorders require how many copies of the mutated gene for disease manifestation?

Autosomal recessive disorders require how many copies of the mutated gene for disease manifestation?

• A. One copy of the mutated gene is sufficient for disease manifestation.
• B. Two copies of the mutated gene are required for the disease to manifest.
• C. Only one copy on the Y chromosome is involved.
• D. Two copies of the normal allele are required for disease to manifest.

Answer: (B)

Autosomal recessive disorders manifest only when both copies of the gene are mutated. Each person has two autosomal copies of most genes, and a single normal copy usually provides enough gene product to maintain normal function. When one copy is mutated and the other is normal, the individual is typically asymptomatic and acts as a carrier. Disease arises only when both copies carry mutations, either the same mutation on each chromosome or two different mutations in the same gene, leading to a loss of enough gene product to cause symptoms. This is why such conditions can skip generations and affect males and females equally. The idea that a single copy on the Y chromosome is involved doesn’t apply to autosomal genes, and having two normal copies would not produce disease.

Autosomal recessive disorders manifest only when both copies of the gene are mutated. Each person has two autosomal copies of most genes, and a single normal copy usually provides enough gene product to maintain normal function. When one copy is mutated and the other is normal, the individual is typically asymptomatic and acts as a carrier. Disease arises only when both copies carry mutations, either the same mutation on each chromosome or two different mutations in the same gene, leading to a loss of enough gene product to cause symptoms. This is why such conditions can skip generations and affect males and females equally. The idea that a single copy on the Y chromosome is involved doesn’t apply to autosomal genes, and having two normal copies would not produce disease.