Which type of inheritance does Hemophilia A fall into?

• A. X-linked dominant
• B. X-linked recessive
• C. Autosomal dominant
• D. Autosomal recessive

Answer: (B)

Hemophilia A is classified as an X-linked recessive disorder, which means that the gene responsible for this condition is located on the X chromosome and that two copies of the mutated gene (in the case of females who have two X chromosomes) are typically necessary for the manifestation of the disorder. Males, having only one X chromosome, will exhibit symptoms if they inherit a single copy of the mutated gene. This pattern of inheritance has significant implications for how the condition is passed down through generations, particularly affecting males more frequently than females. Females can be carriers and may pass on the mutated gene to their sons, but they are less likely to express the disorder unless they inherit two copies of the defective gene, which is less common. Understanding this specific mode of inheritance is critical for genetic counseling, risk assessment, and understanding family histories related to Hemophilia A.