What type of inheritance pattern do most of the discussed conditions (like Aniridia, Huntington disease, and Achondroplasia) share?

• A. X-linked Recessive
• B. Autosomal Dominant
• C. Autosomal Recessive
• D. Mitochondrial

Answer: (B)

Most of the conditions mentioned—Aniridia, Huntington disease, and Achondroplasia—share an autosomal dominant inheritance pattern. This means that an individual only needs one copy of the mutated gene from one parent to express the trait or disorder. In autosomal dominant conditions, the presence of a single mutant allele is enough to exhibit the phenotype, regardless of whether the second allele is normal or also mutated.

In the case of Aniridia, the condition is caused by mutations in the PAX6 gene and is characterized by the absence of the iris in the eyes. Since it's autosomal dominant, a child can inherit the condition if one parent carris the mutation.

Huntington disease, which is a neurodegenerative disorder, is also an autosomal dominant condition caused by a repeat expansion in the HTT gene. An individual with just one copy of the mutated gene will inevitably develop symptoms typically in mid-adulthood.

Achondroplasia, a common form of dwarfism, results from mutations in the FGFR3 gene and follows the same inheritance pattern. The condition illustrates the concept that even if the mutation is inherited from just one affected parent, it can manifest in the offspring.

This type of inheritance pattern is characterized by a vertical transmission of