Title: How Genetic Disorders Are Inherited
Headings: How Genetic Disorders Are Inherited
How Genetic Disorders Are Inherited
Understanding Patterns of Inheritance
Patterns of Inheritance
Autosomal Dominant
Autosomal Recessive
X-Linked Dominant
X-Linked Recessive
Mitochondrial
Other Inheritance Patterns
Y-Linked Disorders
Codominance

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25% risk of inheriting both mutations and having the disorder
50% risk of inheriting only one copy and becoming a carrier
25% risk of not inheriting the mutation at all
Examples of autosomal recessive disorders include cystic fibrosis, sickle cell disease, Tay-Sachs disease, and phenylketonuria (PKU). Living With Sickle Cell Disease
X-Linked Dominant
X-linked dominant disorders are caused by mutations in genes on the X (female) chromosome. In females, who have two X chromosomes, it takes a mutation in only one of the two copies of the gene for a disorder to manifest. In males (who have one X chromosome and one Y chromosome), a mutation in only one copy of the gene in each cell is enough to cause the disorder. Most times, males have more severe symptoms of an X-link disorder than females. However, one feature of X-linked inheritance is that fathers cannot pass on these traits to their sons. Fragile X syndrome is an example of an X-linked dominant disorder. X-Linked Recessive
In X-linked recessive disorders, the mutated gene occurs on the X chromosome. Because males have one X chromosome and one Y chromosome, a mutated gene on the X chromosome is enough to cause an X-linked recessive disorder. Females, by contrast, have two X chromosomes, so a mutated gene on one X chromosome usually has less effect on a female because the non-mutated copy on the other largely cancels out the effect.