What are some of the factors that can cause a person to have a single-gene disease or disorder?

Single-gene disorders result from changes in one gene and can be passed down through different inheritance patterns. Mitochondrial and autosomal inheritance patterns describe ways such disorders can be inherited, and mutations can cause them. Having too many X chromosomes is a chromosome-number condition, not a single-gene cause; extra enzymes are not generally a cause of single-gene disorders.

AI-written and checked against the verified answer.