Which inheritance pattern is described as requiring only one copy of a dominant allele to express the disease?

Which inheritance pattern is described as requiring only one copy of a dominant allele to express the disease?

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

Answer: (D)

The pattern shown is autosomal dominant inheritance. In this mode, just one copy of a mutant allele on an autosome is enough to produce the disease phenotype in an individual who carries it, so heterozygotes are affected. This contrasts with autosomal recessive conditions, which need two copies of the mutant allele to manifest. While X-linked and mitochondrial patterns involve different inheritance routes (X-chromosome genes or maternal mitochondrial DNA, respectively), the statement about requiring only one dominant allele is the hallmark of autosomal dominant diseases. Examples like Huntington disease or Marfan syndrome illustrate how a single altered autosomal allele can drive the trait across sexes.

The pattern shown is autosomal dominant inheritance. In this mode, just one copy of a mutant allele on an autosome is enough to produce the disease phenotype in an individual who carries it, so heterozygotes are affected. This contrasts with autosomal recessive conditions, which need two copies of the mutant allele to manifest. While X-linked and mitochondrial patterns involve different inheritance routes (X-chromosome genes or maternal mitochondrial DNA, respectively), the statement about requiring only one dominant allele is the hallmark of autosomal dominant diseases. Examples like Huntington disease or Marfan syndrome illustrate how a single altered autosomal allele can drive the trait across sexes.