Which inheritance pattern requires two copies of a recessive allele, one from each parent, for the disease to manifest?

Which inheritance pattern requires two copies of a recessive allele, one from each parent, for the disease to manifest?

• A. Autosomal recessive disease
• B. Autosomal dominant disease
• C. X-linked disorder
• D. Mitochondrial inheritance

Answer: (A)

Two copies of a recessive allele, one from each parent, are required for the disease to manifest when the gene is autosomal recessive. In this pattern, an individual must be homozygous recessive to show the disorder; those with one recessive allele are typically carriers and not affected. If both parents are carriers, each child has a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of being unaffected. This contrasts with autosomal dominant diseases, which show symptoms with just one mutant allele, X-linked disorders that involve genes on the X chromosome and often affect males, and mitochondrial inheritance, which comes from the mother and can affect all her children. So, the described inheritance pattern is autosomal recessive disease.

Two copies of a recessive allele, one from each parent, are required for the disease to manifest when the gene is autosomal recessive. In this pattern, an individual must be homozygous recessive to show the disorder; those with one recessive allele are typically carriers and not affected. If both parents are carriers, each child has a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of being unaffected. This contrasts with autosomal dominant diseases, which show symptoms with just one mutant allele, X-linked disorders that involve genes on the X chromosome and often affect males, and mitochondrial inheritance, which comes from the mother and can affect all her children. So, the described inheritance pattern is autosomal recessive disease.