What type of inheritance exhibits variable penetrance and expressivity?

Variable penetrance and expressivity are hallmark features of certain genetic disorders, particularly those linked to autosomal dominant inheritance. In this mode of inheritance, a single copy of an altered gene is sufficient to cause the disorder, yet not all individuals who inherit the mutation exhibit the phenotype associated with the gene mutation due to penetrance variability. This means that some individuals may show the condition fully, while others may have only mild symptoms, or none at all, despite carrying the mutation.

Expressivity refers to the degree of phenotypic expression of the genotype, which can vary widely among individuals. For autosomal dominant disorders, different individuals may display different symptoms or severities of symptoms, further emphasizing the concept of variable expressivity. Examples include conditions like Marfan syndrome or Huntington's disease, where the full range of phenotypic effects may vary considerably from one person to another.

In contrast, other inheritance patterns like autosomal recessive, X-linked recessive, or inherited syndromic conditions tend to have more uniform expression or pedigree-like traits, which do not exhibit the same level of variability in penetrance or expressivity as observed in autosomal dominant disorders.